Conductive aniline polymer, method for producing same, and method for producing conductive film

ABSTRACT

When measuring the molecular mass distribution of conductive aniline polymer of formula (1) by GPC and converting its retention time into molecular mass (M) in terms of sodium polystyrene sulfonate, for the molecular mass (M), the area ratio (X/Y) of the area (X) of a region of 15,000 Da or more to the area (Y) of a region of less than 15,000 Da is 1.20 or more. A method for producing such a polymer includes: polymerization step (Z1) where specific aniline derivative (A) is polymerized in a solution containing basic compound (B), solvent (C), and oxidizing agent (D) at a liquid temperature lower than 25° C.; or polymerization step (Z2) where specific aniline derivative (A) and oxidizing agent (D) are added to and polymerized in a solution of a conductive aniline polymer (P-1) with a unit of formula (1) dissolved or dispersed in a solvent (C).

TECHNICAL FIELD

The present invention relates to a conductive aniline polymer, a methodfor producing the same, and a method for producing a conductive film.

This application claims the priority based upon Japanese PatentApplication No. 2010-240039 filed on Oct. 26, 2010, Japanese PatentApplication No. 2011-006849 filed on Jan. 17, 2011, Japanese PatentApplication No. 2011-032053 filed on Feb. 17, 2011, Japanese PatentApplication No. 2011-071517 filed on Mar. 29, 2011, and Japanese PatentApplication No. 2011-083579 filed on Apr. 5, 2011, the contents of whichare incorporated herein by reference.

BACKGROUND ART

As a conductive polymer for various applications, a conductivesulfonated polyaniline polymer has been known.

As a method for producing a sulfonated polyaniline, for example, PatentLiterature 1 discloses a method for producing an aniline copolymer, themethod including copolymerizing alkoxy group-substitutedaminobenzenesulfonic acid with at least one compound selected from thegroup consisting of aniline, N-alkylaniline, and phenylene diamines.

However, a copolymer obtained by the method described in PatentLiterature 1 has a low rate of sulfonation and a low solubility in wateralone, and therefore causes a problem of poor workability. In addition,the copolymer has a problem of low conductivity due to difficulty inpurification and the presence of impurities.

In order to overcome these problems, as a polyaniline in which an acidicgroup is introduced in all the aromatic rings and a method for producingsuch a polyaniline, Patent Literatures 2 and 3 each disclose a solubleconductive aniline polymer and a method for producing such a solubleconductive aniline polymer. The method includes: dissolving an acidicgroup-substituted aniline such as a sulfonic acid group-substitutedaniline or a carboxy group-substituted aniline in a solution containinga basic compound; and adding dropwise an oxidizing agent to the solutionto polymerize the aniline.

Contrary to the conventional established theory that it is difficult topolymerize anilines alone having a sulfonic acid group or a carboxygroup, the method enables production of a high molecular mass polymer.In addition, the obtained conductive polymer exhibits excellentsolubility in both acidic and alkaline aqueous solutions. Therefore, aconductive polymer having an advantage in terms of processing can beproduced relatively easily from an inexpensive starting material.

Patent Literature 4 discloses a method capable of improving conductivityand solubility. In the method, an acidic group-substituted aniline suchas a sulfonic acid group-substituted aniline or a carboxygroup-substituted aniline is polymerized using an oxidizing agent in amixed solution of a basic compound and a water-soluble organic solvent,and the resultant polymer is subjected to acid treatment to be improvedin conductivity and solubility.

Patent Literature 5 discloses a method of oxidation polymerization. Inthe method, an acidic group-substituted aniline such as a sulfonic acidgroup-substituted aniline and/or a carboxy group-substituted aniline isdissolved in a solution containing a basic compound. The resultingsolution is then added dropwise to an oxidizing agent to make a reactionsystem in which the molar amount of the oxidizing agent is equal to ormore than that of the aniline, to perform oxidization polymerization.

Patent Literature 6 discloses a method for purifying a solution ofpolyaniline derivative in coexistence with a dopant of impurities bydialysis or ultrafiltration.

However, according to the methods of Patent Literatures 2 and 3, the pHin a system at the initial stage of polymerization is basic. As aresult, a side reaction such as conversion of acidic group-substitutedaniline as a starting material monomer to an azo compound is notsufficiently suppressed. Therefore, a byproduct contained in the polymerprevents the improvement of conductivity.

The methods of Patent Literatures 4 to 6 suppress a side reaction suchas conversion of acidic group-substituted aniline as a starting materialmonomer to an azo compound. However, impurities cannot be removedsufficiently during separation of polymer from a polymerization reactionsolution by filtration. Therefore, the resultant polymer cannotnecessarily satisfy conductive performance as compared with the otherconductive polymers.

The conductivity (σ) of a conductive polymer generally depends on thenumber (η) of carriers, the charge (q) of the carriers, and the mobility(μ) of the carriers between and in molecular chains.

In the case of a soluble conductive aniline polymer, the charge (q) ofcarriers is a characteristic value determined by the type of thecarriers. Therefore, increasing both the number (η) and mobility (μ) ofthe carriers is essential for improvement of the conductivity. Increaseof the molecular mass of the polymer, increase of the molecular mass ofthe polymer by removal of an unreacted monomer, an oligomer as abyproduct, and impurities, and the like are considered to be effectivefor the increase of the mobility (μ).

For example, Patent Literatures 7 and 8 disclose that an unreactedmonomer and a low molecular mass substance are removed from a solubleconductive aniline polymer to improve the conductivity.

CITATION LIST Patent Literatures

-   Patent Literature 1: JP-A 6-293828-   Patent Literature 2: JP-A 7-196791-   Patent Literature 3: JP-A 7-324132-   Patent Literature 4: JP-A 10-110030-   Patent Literature 5: JP-A-2000-219739-   Patent Literature 6: JP-A 10-259249-   Patent Literature 7: JP-T-2001-513126-   Patent Literature 8: JP-A-2010-202836

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the production method described in Patent Literature 7 and 8are difficult to mass-produce a conductive aniline polymer having a highmolecular mass and high conductivity.

In general, further, a low yield is a matter of concern with respect tothe method described in Patent Literature 8. In this method,furthermore, this is another matter of concern. That is, the viscosityof polymer increases as the molecular mass of the polymer increases, andthus a decrease of productivity or the like may occur.

In view of the circumstances, an object of the present invention is toprovide a conductive aniline polymer having high conductivity, a methodfor mass-producing the conductive aniline polymer having highconductivity, and a method for producing a conductive film having highconductivity.

Solutions to the Problems

The present invention has the following aspects:

[1] A conductive aniline polymer has a repeating unit represented by theformula (1) described below, and has an area ratio (X/Y) of 1.20 ormore, which is calculated by an evaluation process including thefollowing steps (I) to (VI):

(I) preparing a test solution by dissolving a conductive aniline polymerin an eluent adjusted to pH 10 or more so that the conductive anilinepolymer has a solid content concentration of 0.1% by mass;

(II) subjecting the test solution to a polymer materials evaluationsystem equipped with a gel permeation chromatograph to determine amolecular mass distribution of the test solution to obtain achromatogram thereof;

(III) converting a retention time in the chromatogram obtained in thestep (II) to a molecular mass (M) in terms of sodium polystyrenesulfonate;

(IV) determining the area (X) of a region having a molecular mass (M) of15,000 Da or more in the converted molecular mass (M) in terms of sodiumpolystyrene sulfonate;

(V) determining the area (Y) of a region having a molecular mass (M) ofless than 15,000 Da in the converted molecular mass (M) in terms ofsodium polystyrene sulfonate; and

(VI) determining the area ratio (X/Y) of the area (X) to the area (Y).

In the formula (1), R¹ to R⁴ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R¹ to R⁴ is an acidic group or a salt thereof. Herein, theacidic group is a sulfonic acid group or a carboxyl group.

[2] A method for producing the conductive aniline polymer as describedin [1] includes a polymerization step (Z1) where an aniline derivative(A) represented by the following formula (2) is polymerized in asolution containing a basic compound (B), a solvent (C), and anoxidizing agent (D) at a temperature lower than 25° C.:

In the formula (2), R⁵ to R⁹ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R⁵ to R⁹ is an acidic group or a salt thereof. Herein, theacidic group is a sulfonic acid group or a carboxyl group.

[3] In the method for producing a conductive aniline polymer asdescribed in [2], the solvent (C) contains 35% by volume or more ofwater relative to the entire volume of the solvent (C).[4] A method for producing the conductive aniline polymer as describedin [1] includes a polymerization step (Z2) where an aniline derivative(A) represented by the following formula (2) and an oxidizing agent (D)are added to and polymerized in a solution in which a conductive anilinepolymer (P-1) having a repeating unit represented by the above formula(1) is dissolved in a solvent (C) or added to and polymerized in adispersion in which the conductive aniline polymer (P-1) is dispersed inthe solvent (C):

In the formula (2), R⁵ to R⁹ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R⁵ to R⁹ is an acidic group or a salt thereof. Herein, theacidic group means a sulfonic acid group or a carboxyl group.

[5] In the method for producing a conductive aniline polymer asdescribed in [4], the solvent (C) contains 35% by volume or more ofwater relative to the entire volume of the solvent (C).[6] The method for producing a conductive aniline polymer as describedin any one of [2] to [5] further includes purifying a solutioncontaining a product obtained in the polymerization step (Z1) or (Z2) bymembrane filtration.[7] The method for producing a conductive aniline polymer described inany one of [2] to [5] further includes purifying a solution containing aproduct obtained in the polymerization step (Z1) or (Z2) byprecipitation.[8] The method for producing a conductive aniline polymer described in[7] further includes purifying a solution containing a purifiedsubstance obtained in the precipitation purification step by membranefiltration.[9] A method for producing a conductive film further includes applying asolution containing the conductive aniline polymer described in [1] to abase material and drying the solution applied to the base material.

Effects of the Invention

The conductive aniline polymer of the present invention has highconductivity.

According to the method for producing a conductive aniline polymer ofthe present invention, a conductive aniline polymer having highconductivity can be mass-produced.

According to the method for producing a conductive film of the presentinvention, a conductive film having high conductivity can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating one example of chromatogram obtained bygel permeation chromatography in the step (II) of the evaluationprocess.

DESCRIPTION OF EMBODIMENTS

The present invention will be described in detail below.

In the present invention, the term “conductivity” means that a substancehas a volume resistivity of 10⁹ Ω·cm or less.

Further, the term “molecular mass (M)” means a mass average molecularmass (Mw).

<Conductive Aniline Polymer>

The conductive aniline polymer of the present invention (hereinafteralso simply referred to as “polymer”) has a unit represented by thefollowing formula (1):

In the formula (1), R¹ to R⁴ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R¹ to R⁴ is an acidic group or a salt thereof.

Herein, the acidic group means a sulfonic acid group or a carboxylgroup. Therefore, in the formula (1), at least one of R¹ to R⁴ is —SO₃H,—S₃ ⁻, —COOH, or —COO⁻. The term “salt of an acidic group” is any of analkali metal salt, an ammonium salt, and a substituted ammonium salt ofthe acidic group.

The conductive aniline polymer preferably contains a repeating unitrepresented by the formula (1) in an amount of 20 to 100% by mole, andmore preferably 50 to 100% by mole, relative to all the repeating units(100% by mole) constituting the conductive aniline polymer. The amountof the repeating unit is particularly preferably 100% by mole since thesolubility in water and an organic solvent is excellent regardless ofpH.

The conductive aniline polymer preferably contains 10 or more repeatingunits represented by the formula (1) in one molecule from the viewpointof excellent conductivity.

The conductive aniline polymer is preferably a compound having aphenylenediamine structure (reduced form) and a quinonediimine structure(oxidized form), represented by the following formula (3):

In the formula (3), R¹⁰ to R²⁵ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R¹⁰ to R²⁵ is an acidic group.

Further, “n” represents a degree of polymerization.

For the above substituents, in particular, each of at least two of foursubstituents of each aromatic ring preferably has an acidic group or analkoxy group.

The phenylenediamine structure (reduced form) and quinonediiminestructure (oxidized form) of the compound can be reversibly converted byoxidation or reduction at any ratio. The ratio (m) of thephenylenediamine structure to the quinodiimine structure preferablyfalls within a range of 0.2<m<0.8, and more preferably 0.3<m<0.7, fromthe viewpoint of conductivity and solubility.

The conductive aniline polymer of the present invention has an arearatio (X/Y) of 1.20 or more, which is calculated by an evaluationprocess including the following steps (I) to (VI):

(I) preparing a test solution by dissolving a conductive aniline polymerin an eluent adjusted to pH 10 or more so that the conductive anilinepolymer has a solid content concentration of 0.1% by mass;

(II) subjecting the test solution to a polymer materials evaluationsystem equipped with a gel permeation chromatograph to determine themolecular mass distribution of the test solution to obtain achromatogram thereof;

(III) converting a retention time in the chromatogram obtained in thestep (II) to a molecular mass (M) in terms of sodium polystyrenesulfonate;

(IV) determining the area (X) of a region having a molecular mass (M) of15,000 Da or more in the converted molecular mass (M) in terms of sodiumpolystyrene sulfonate;

(V) determining the area (Y) of a region having a molecular mass (M) ofless than 15,000 Da in the converted molecular mass (M) in terms ofsodium polystyrene sulfonate; and

(VI) determining the area ratio (X/Y) of the area (X) to the area (Y).

The step (I) is a step of dissolving a conductive aniline polymer in aneluent to prepare a test solution.

The eluent is a solution in which a solute is dissolved in a solvent.Examples of the solvent include water, acetonitrile, alcohols (e.g.,methanol and ethanol), dimethylformamide, dimethylsulfoxide, and a mixedsolvent thereof.

Examples of the solute include sodium carbonate, sodium hydrogencarbonate, sodium dihydrogen phosphate, trisodium phosphate, disodiumhydrogen phosphate, glycine, sodium hydroxide, potassium chloride, andboric acid.

The pH of the eluent used in the step (I) is 10 or more. Thequantitative value may vary when the pH is less than 10. An eluent ofpH10 of pH10 or more can be used to obtain stable measurement results.

For example, the eluent of pH10 or more can be prepared as follows:Water (ultra-pure water) and methanol are mixed at a volume ratio ofwater to methanol of 8 to 2, to obtain a mixed solvent. Then, sodiumcarbonate and sodium hydrogen carbonate are added to the resultant mixedsolvent so that the solid content concentrations thereof are 20 mmol/Land 30 mmol/L, respectively, to obtain an eluent.

The resulting eluent has a pH of 10.8 at 25° C.

The pH of the eluent is a value measured by a pH meter while maintainingthe temperature of the eluent held at 25° C.

A method for preparing the eluent of pH10 or more is not limited to theprocess described above. For example, sodium carbonate having a solidcontent concentration of 20 mmol/L and sodium hydrogen carbonate havinga solid content concentration of 30 mmol/L may be separately prepared byusing a mixed solvent of water and methanol (water:methanol=8:2), andthen mixed to prepare an eluent.

A conductive aniline polymer in a solid state may be added to anddissolved in an eluent as long as the solid content concentrationthereof reaches 0.1% by mass at the time of the addition of the polymerto the eluent. Alternatively, a conductive aniline polymer is dissolvedin a solvent to prepare a conductive aniline polymer solution inadvance, and the resulting solution may be then added to an eluent. Whenthe solid content concentration of the conductive aniline polymer in thetest solution is 0.1% by mass, the eluent exerts its pH buffer action,sufficiently. As a result, stable measurement results are obtained.

When the conductive aniline polymer solution is used, the solid contentconcentration of the conductive aniline polymer solution is notparticularly limited as long as the solid content concentration of theconductive aniline polymer reaches 0.1% by mass or more at the time ofat the time of the addition of the solution to the eluent. However, thesolid content concentration is preferably 1.0% by mass or more. When thesolid content concentration of the conductive aniline polymer solutionis less than 1.0% by mass, the pH buffer action of the eluent is notsufficiently exerted during addition of the solution to the eluent. As aresult, the pH of the test solution becomes less than 10, thequantitative value is varied, and stable measurement results are hardlyobtained.

Examples of the solvent used for the conductive aniline polymer solutioninclude solvents wherein a conductive aniline polymer can be dissolved,as described below. In particular, water is preferable.

The step (II) is a step of measuring the molecular mass distribution ofthe test solution by a polymer materials evaluation system through gelpermeation chromatography (GPC).

The polymer materials evaluation system is equipped with a gelpermeation chromatograph. The system can separate compounds (e.g.,polymer, oligomer, and monomer) from one another according to theirmolecular masses, followed by analyzing the compounds.

A detector such as a photodiode array detector or a UV detector isconnected to the gel permeation chromatograph.

In the step (II), for example, a chromatogram shown in FIG. 1 can beobtained by GPC.

In the chromatogram shown in FIG. 1, a vertical axis is an absorbance,and a horizontal axis is a retention time. A higher molecular masssubstance is detected at a relatively short retention time, while alower molecular mass substance is detected at a relatively longretention time.

The step (III) is a step of converting the retention time in thechromatogram obtained in the step (II) to a molecular mass (M) in termsof sodium polystyrene sulfonate.

Specifically, sodium polystyrene sulfonate having each peak topmolecular mass of 206, 1,030, 4,210, 13,500, 33,500, 78,400, 158,000,and 2,350,000 is used as a standard sample. Similarly to the testsolution, each standard sample is dissolved in an eluent so that thesolid content concentration is 0.05% by mass, provided that the solidcontent concentration of the standard sample having a peak top molecularmass of 206 is 25 ppm, to prepare each standard solution. A relationbetween the retention time and the molecular mass in each standardsolution is determined by GPC, and a calibration curve is made. From themade calibration curve, the retention time in the chromatogram obtainedin the step (II) is converted to a molecular mass (M) in terms of sodiumpolystyrene sulfonate.

The step (IV) is a step of determining the area (X) of a region (x)where having a molecular weight molecular mass (M) of 15,000 Da or more,as shown in FIG. 1, in the converted molecular mass (M) in terms ofsodium polystyrene sulfonate.

The step (V) is a step of determining the area (Y) of a region (y)having a molecular mass (M) of less than 15,000 Da.

The step (VI) is a step of determining the area ratio (X/Y) of the area(X) to the area (Y).

The conductive aniline polymer of the present invention has an arearatio (X/Y) of 1.20 or more, which is calculated by the evaluationprocess described above. When the area ratio is 1.20 or more, theconductive aniline polymer has high conductivity. This reason isconsidered as follows.

A conductive aniline polymer often contains a low molecular masssubstance such as an oligomer, an unreacted monomer, and impuritiesproduced as byproduct in the production process of the polymer. The lowmolecular mass substance is considered to cause a decrease inconductivity.

An area (Y) is the area of a region having a molecular mass (M) of lessthan 15,000 Da. There may be mainly low molecular mass substance such asan oligomer, a monomer, and impurities in this region. When the arearatio (X/Y) is 1.20 or more, the proportion of the low molecular masssubstance contained in the conductive aniline polymer is low. In thiscase, the molecular mass of the conductive aniline polymer is high, andtherefore the conductive aniline polymer has high conductivity.

As the area ratio (X/Y) is larger, the proportion of the low molecularmass substance in the conductive aniline polymer is lower. Therefore, alarger area ratio (X/Y) is preferable. Specifically, the area ratio ispreferably 1.40 or more, more preferably 1.70 or more, and particularlypreferably 2.00 or more.

Since the conductive aniline polymer of the present invention has a highmolecular mass, the conductivity as well as the thermal resistance isexcellent.

The conductive aniline polymer is used for various applications such asa condenser as described in detail below. For example, when theconductive aniline polymer is used for a condenser, a conductive layerof the condenser is usually formed by applying the conductive anilinepolymer to a metal electrode and drying it by heating at a predeterminedtemperature. Since the conductive aniline polymer of the presentinvention has excellent thermal resistance, it is suitable forapplications such as a condenser in which the production processincludes a step of drying by heating.

According to the following method, a conductive aniline polymer having arepeating unit represented by the formula (1) and an area ratio (X/Y) of1.20 or more can be produced. The term “purification” used herein meansremoval of a low molecular mass substance such as a monomer, anoligomer, and impurities.

<Method for Producing Conductive Aniline Polymer>

The method for producing a conductive aniline polymer according to thepresent invention includes a polymerization step (Z).

First Embodiment

In this embodiment, a polymerization step (Z1) shown below is used asthe polymerization step (Z).

The method for producing a conductive aniline polymer of the embodimentincludes a polymerization step (Z1) of polymerizing an anilinederivative (A) in a solution containing a basic compound (B), a solvent(C), and an oxidizing agent (D) at a liquid temperature lower than 25°C.

Hereinafter, each component used in the polymerization step (Z1) will bespecifically described.

Aniline Derivative (A)

An aniline derivative (A) used in the polymerization step (Z1) of theembodiment is a compound represented by the following formula (2).Specifically, the aniline derivative (A) is preferably a compoundselected from the group consisting of an acidic group-substitutedaniline, an alkali metal salt, an alkaline earth metal salt, an ammoniumsalt, and a substituted ammonium salt thereof.

In the formula (2), R⁵ to R⁹ are each independently —H, a linear orbranched alkyl group having 1 to 24 carbon atoms, a linear or branchedalkoxy group having 1 to 24 carbon atoms, an acidic group or a saltthereof, a hydroxy group, a nitro group, —F, —Cl, —Br, or —I; and atleast one of R⁵ to R⁹ is an acidic group or a salt thereof.

Typical examples of the compound represented by the formula (2) includea sulfonic acid group-substituted aniline and a carboxygroup-substituted aniline. Among them, a compound having acidic groupsin the o- or m-position to the amino group is preferable from theviewpoint of conductivity and solubility of the obtained polymer.

Typical examples of the sulfonic acid group-substituted aniline includean aminobenzenesulfonic acid derivative. On the other hand, typicalexamples of the carboxy group-substituted aniline include anaminobenzoic acid derivative. Among them, the aminobenzenesulfonic acidderivative tends to have higher conductivity as compared with theaminobenzoic acid derivative, while the aminobenzoic acid derivativetends to have higher solubility as compared with theaminobenzenesulfonic acid derivative. These derivatives may be used as amixture thereof in any ratio according to the purpose.

Preferable examples of the aminobenzenesulfonic acid derivative includeo-, m-, and p-aminobenzenesulfonic acids, aniline-2,6-disulfonic acid,aniline-2,5-disulfonic acid, aniline-3,5-disulfonic acid,aniline-2,4-disulfonic acid, and aniline-3,4-disulfonic acid.

Examples of the sulfonic acid group-substituted aniline other than theaminobenzenesulfonic acid derivative include alkyl group-substitutedaminobenzenesulfonic acids such as methylaminobenzenesulfonic acid,ethylaminobenzenesulfonic acid, n-propylaminobenzenesulfonic acid,isopropylaminobenzenesulfonic acid, n-butylaminobenzenesulfonic acid,sec-butylaminobenzenesulfonic acid, and tert-butylaminobenzenesulfonicacid; alkoxy group-substituted aminobenzenesulfonic acids such asmethoxyaminobenzenesulfonic acid, ethoxyaminobenzenesulfonic acid, andpropoxyaminobenzenesulfonic acid; hydroxy group-substitutedaminobenzenesulfonic acids; nitro group-substituted aminobenzenesulfonicacids; and halogen group-substituted aminobenzenesulfonic acids such asfluoroaminobenzenesulfonic acid, chloroaminobenzenesulfonic acid, andbromoaminobenzenesulfonic acid. Among them, alkyl group-substitutedaminobenzenesulfonic acids, hydroxy group-substitutedaminobenzenesulfonic acids, and halogen group-substitutedaminobenzenesulfonic acids are preferable in practical use from theviewpoint of conductivity, solubility and the like of the obtainedpolymer.

These sulfonic acid group-substituted anilines may be used alone or as amixture of two or more (containing an isomer) in any ratio.

Preferable examples of the aminobenzoic acid derivative include o-, m-,and p-aminobenzenecarboxylic acids, aniline-2,6-dicarboxylic acid,aniline-2,5-dicarboxylic acid, aniline-3,5-dicarboxylic acid,aniline-2,4-dicarboxylic acid, and aniline-3,4-dicarboxylic acid.

Examples of the carboxy group-substituted aniline other than theaminobenzoic acid derivative include alkyl group-substitutedaminobenzenecarboxylic acids such as methylaminobenzenecarboxylic acid,ethylaminobenzenecarboxylic acid, n-propylaminobenzenecarboxylic acid,isopropylaminobenzenecarboxylic acid, n-butylaminobenzenecarboxylicacid, sec-butylaminobenzenecarboxylic acid, andtert-butylaminobenzenecarboxylic acid; alkoxy group-substitutedaminobenzenecarboxylic acids such as methoxyaminobenzenecarboxylic acid,ethoxyaminobenzenecarboxylic acid, and propoxyaminobenzenecarboxylicacid; hydroxy group-substituted aminobenzenecarboxylic acids; nitrogroup-substituted aminobenzenecarboxylic acids; and halogengroup-substituted aminobenzenecarboxylic acids such asfluoroaminobenzenecarboxylic acid, chloroaminobenzenecarboxylic acid,and bromoaminobenzenecarboxylic acid. Among them, alkylgroup-substituted aminobenzenecarboxylic acids, alkoxy group-substitutedaminobenzenecarboxylic acids, and halogen group-substitutedaminobenzenecarboxylic acids are preferable in practical use from theviewpoint of conductivity, solubility and the like of the obtainedpolymer.

These carboxy group-substituted anilines may be used alone or as amixture of two or more (containing an isomer) in any ratio.

The compound represented by the formula (2) can be expressed as any of asulfonic acid group-substituted alkylaniline, a carboxygroup-substituted alkylaniline, a sulfonic acid group-substitutedalkoxyaniline, a carboxy group-substituted alkoxyaniline, a sulfonicacid group-substituted hydroxyaniline, a carboxy group-substitutedhydroxyaniline, a sulfonic acid group-substituted nitroaniline, acarboxy group-substituted nitroaniline, a sulfonic acidgroup-substituted fluoroaniline, a carboxy group-substitutedfluoroaniline, a sulfonic acid group-substituted chloroaniline, acarboxy group-substituted chloroaniline, a sulfonic acidgroup-substituted bromoaniline, and a carboxy group-substitutedbromoaniline. Specific examples of the positions of these substituentsand the combinations of the substituents are shown in Table 1.

TABLE 1 R¹ R² R³ R⁴ R⁵ A B H H H A H B H H A H H B H A H H H B H A B H HH A H B H H A H H H B A H H B H H A B H H H A H B B H A H H H B A H H HH H A B H H B A H H B H A H B H H A H H H H B A H H B H A H B H H A B HH H A

Symbols shown in Table 1 are as follows:

“A” shows one group selected from a sulfonic acid group or a carboxygroup, and an alkali metal salt, an alkaline earth metal salt, anammonium salt, and a substituted ammonium salt thereof.

“B” shows one group selected from an alkyl group such as a methyl group,an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, asec-butyl group, and a tert-butyl group, an alkoxy group such as amethoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group,a n-buthoxy group, a sec-buthoxy group, and a tert-buthoxy group, ahydroxy group, and a halogen group such as a fluoro group, a chlorogroup, and a bromo group.

“H” shows hydrogen.

Examples of an alkaline metal capable of forming a salt with the acidicgroup-substituted anilines include lithium, sodium, potassium, andcesium.

Examples of an alkaline earth metal capable of forming a salt with theacidic group-substituted anilines include magnesium and calcium.

Examples of the substituted ammonium include alicyclic ammoniums, cyclicsaturated ammoniums, and cyclic unsaturated ammoniums.

Examples of the alicyclic ammoniums include an ammonium represented bythe following formula (4):

In the formula (4), R²⁶ to R²⁹ are each independently —H or an alkylgroup having 1 to 4 carbon atoms.

Examples of such alicyclic ammoniums include methylammonium,dimethylammonium, trimethylammonium, ethylammonium, diethylammonium,triethylammonium, methylethylammonium, diethylmethylammonium,dimethylethylammonium, propylammonium, dipropylammonium,isopropylammonium, diisopropylammonium, butylammonium, dibutylammonium,methylpropylammonium, ethylpropylammonium, methylisopropylammonium,ethylisopropylammonium, methylbutylammonium, ethylbutylammonium,tetramethylammonium, tetramethylolammonium, tetraethylammonium,tetra-n-butylammonium, tetra-sec-butylammonium, andtetra-tert-butylammonium. In particular, in view of conductivity andsolubility of the obtained polymer, the case where two of R²⁶ to R²⁹ inthe formula (4) are hydrogens and the other two are alkyl groups having1 to 4 carbon atoms is more preferable, and the case where one of R²⁶ toR²⁹ is hydrogen and the other three are alkyl groups having 1 to 4carbon atoms is most preferable.

Examples of the cyclic saturated ammoniums include piperidinium,pyrrolidinium, morpholinium, piperazinium, and derivatives having theseskeletons.

Examples of the cyclic unsaturated ammoniums include pyridinium,α-picolinium, β-picolinium, γ-picolinium, quinolinium, isoquinolinium,pyrrolinium, and derivatives having these skeletons.

As described in detail below, when a mixed solution of an anilinederivative (A) and a basic compound (B) is added dropwise to anoxidizing agent solution in the polymerization step (Z1), theconcentration of the aniline derivative (A) in a reaction solution aftercompletion of the dropwise addition is preferably 1 to 90% by mass, andmore preferably 5 to 70% by mass from the viewpoint of reactivity.

When the concentration of the aniline derivative (A) in the reactionsolution is lower than the above-described range, the reaction rate islowered, and as a result, it takes a long time to complete the reaction.In contrast, when the concentration of the aniline derivative (A) in thereaction solution exceeds the range, the aniline derivative (A) may beprecipitated in the reaction solution. As a result, a polymerizationreaction may not proceed sufficiently.

However, when the concentration of the aniline derivative (A) in thereaction solution falls within the above-described range, a sufficientreaction rate is maintained, and therefore a polymer having highconductivity can be produced with good productivity.

Basic Compound (B)

Examples of the basic compound (B) used in the polymerization step (Z1)of the embodiment include an inorganic base, ammonia, alicyclic amines,cyclic saturated amines, and cyclic unsaturated amines.

Examples of the inorganic base include a salt of hydroxide such assodium hydroxide, potassium hydroxide, lithium hydroxide, magnesiumhydroxide, and calcium hydroxide. In particular, sodium hydroxide ispreferable in practical use from the viewpoint of conductivity andsolubility of the obtained polymer.

Examples of alicyclic amines include a compound represented by thefollowing formula (5) and an ammonium hydroxide compound represented bythe following formula (6):

In the formula (5), R³⁰ to R³² are each independently an alkyl grouphaving 1 to 4 carbon atoms.

In the formula (6), R³³ to R³⁵ are each independently a hydrogen atom oran alkyl group having 1 to 4 carbon atoms.

Examples of cyclic saturated amines include piperidine, pyrrolidine,morpholine, piperazine, derivatives having these skeletons, and ammoniumhydroxide compounds thereof.

Examples of cyclic unsaturated amines include pyridine, α-picoline,β-picoline, γ-picoline, quinoline, isoquinoline, pyrroline, derivativeshaving these skeletons, and ammonium hydroxide compounds thereof.

The basic compound (B) is preferably an inorganic base. Preferableexamples of a basic compound to be used other than the inorganic baseinclude methylamine, dimethylamine, trimethylamine, ethylamine,diethylamine, triethylamine, ethylmethylamine, ethyldimethylamine,diethylmethylamine, pyridine, α-picoline, β-picoline, and γ-picoline.

When the inorganic salt or such basic compound is used, a polymer havinghigh conductivity and high purity can be obtained.

These basic compounds may be used alone or as a mixture of two or morein any ratio.

When the basic compound (B) is used as a solution, the concentrationthereof is preferably 0.1 mol/L or more, more preferably 0.1 to 10.0mol/L, and further preferably 0.2 to 8.0 mol/L. When the concentrationof the basic compound (B) is 0.1 mol/L or more, a polymer can beobtained in a high yield. On the other hand, when the concentration ofthe basic compound (B) is 10.0 mol/L or less, the conductivity of apolymer to be obtained tends to be improved.

From the viewpoint of conductivity, the mass ratio of the anilinederivative (A) to the basic compound (B) is preferably 1:100 to 100:1,and more preferably 10:90 to 90:10.

When the proportion of the basic compound (B) is low, the solubility ina solvent (C) described below is lowered. As a result, the reactivity islowered, and therefore the conductivity of a polymer to be obtained maybe lowered. In contrast, when the proportion of the basic compound (B)is high, a salt is easily formed from an acidic group in a polymer to beobtained and the basic compound (B). Thus, the conductivity of thepolymer may be lowered.

Therefore, when the proportion of the basic compound (B) falls within apreferable range, the solubility in a solvent (C) and the reactivity ofthe basic compound (B) are improved, and the conductivity of the polymeris improved.

Solvent (C)

Examples of a solvent (C) used in the polymerization step (Z1) of theembodiment include water, and a mixed solvent of water and awater-soluble organic solvent.

The water-soluble organic solvent is not limited as long as it can bemixed in water. From the viewpoint of low cost and easy availability,examples thereof include methanol, ethanol, 2-propanol, acetone,acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, propyleneglycol, and ethylene glycol. In particular, from the viewpoint ofsolubility of an aniline derivative (A) and an oxidizing agent describedbelow, acetone and acetonitrile are more preferably used.

As the solvent (C), water alone is preferably used. When a mixed solventof water and a water-soluble organic solvent is used, the content ofwater in the solvent (C) is preferably 35% by volume or more, and morepreferably 40% by mass or more, relative to the entire volume of thesolvent (C). When the content of water in the solvent (C) is 35% byvolume or more, the precipitation of the aniline derivative (A) and theoxidizing agent described below can be suppressed. Therefore, thepolymerization reaction of the aniline derivative (A) proceedssufficiently, and a conductive aniline polymer having a higher molecularmass becomes easier to be produced.

Oxidizing Agent (D)

An oxidizing agent (D) used in the polymerization step (Z1) of theembodiment is not limited as long as it has a standard electrodepotential of 0.6 V or more. From the industrial viewpoint such asrelatively easy availability, examples of the oxidizing agent (D)preferably include peroxodisulfuric acid, salts of peroxodisulfuric acidsuch as ammonium peroxodisulfate, sodium peroxodisulfate, and potassiumperoxodisulfate, and hydrogen peroxide. These oxidizing agents may beused alone or as a mixture of two or more in any ratio.

In addition, it is effective that a transition metal compound such asiron and copper is used as a catalyst together with the oxidizing agent.

The amount of the oxidizing agent (D) to be used is preferably 1 to 5mol, and more preferably 1 to 3 mol, relative to 1 mol of the anilinederivative (A). When the amount of the oxidizing agent (D) to be usedfalls within the above-described range, the molecular mass of a polymercan be sufficiently increased and the main chain can be sufficientlyoxidized.

From the viewpoint of reactivity, it is preferable that polymerizationbe carried out in a system where the molar amount of the oxidizing agent(D) is equal to or more than that of the aniline derivative (A). Whenthe molar amount of the oxidizing agent (D) is less than the equimolaramount, a lot of unreacted substances tend to remain after thepolymerization reaction. When the molar amount of the oxidizing agent(D) is more than the equimolar amount, a lot of byproducts tend to beproduced.

As described in detail below, when a mixed solution of an anilinederivative (A) and a basic compound (B) is added dropwise to anoxidizing agent solution in the polymerization step (Z1), theconcentration of the oxidizing agent (D) in a reaction solution at thestart of dropwise addition is preferably 2 to 90% by mass, and morepreferably 5 to 80% by mass from the viewpoint of reactivity. Theconcentration of the oxidizing agent (D) in the reaction solution aftercompletion of the dropwise addition is preferably 1 to 90% by mass, andmore preferably 2.5 to 40% by mass from the viewpoint of reactivity.

When the concentration of the oxidizing agent (D) in the reactionsolution is low, the reaction rate is lowered, and as a result, it takesa long time to complete the reaction. In contrast, when theconcentration of the oxidizing agent (D) in the reaction solution ishigh, the oxidizing agent (D) may be precipitated in the reactionsolution. As a result, a polymerization reaction may not proceedsufficiently.

However, when the concentration of the oxidizing agent (D) in thereaction solution falls within the above-described range, a sufficientreaction rate is maintained, and therefore a polymer having highconductivity can be produced with good productivity.

Polymerization Step (Z1)

The polymerization step (Z1) of the embodiment is a step of polymerizingthe aniline derivative (A) in a solution containing the basic compound(B), the solvent (C), and the oxidizing agent (D) at a temperature lowerthan 25° C.

Specific examples of a method for polymerizing an aniline derivative (A)include a method for adding dropwise a mixed solution in which ananiline derivative (A) and a basic compound (B) are dissolved in asolvent (C) to an oxidizing agent solution in which an oxidizing agent(D) is dissolved in a solvent (C); a method for adding dropwise anoxidizing agent solution to a mixed solution of an aniline derivative(A) and a basic compound (B); a method for adding dropwise a mixedsolution of an aniline derivative (A) and a basic compound (B) and anoxidizing agent solution to a reaction vessel or the like at the sametime; and a method for continuously supplying a mixed solution of ananiline derivative (A) and a basic compound (B) and an oxidizing agentsolution to a reactor or the like and pushing off them to polymerize theaniline derivative (A). Among these methods, a method for addingdropwise a mixed solution of an aniline derivative (A) and a basiccompound (B) to an oxidizing agent solution is preferable from theviewpoint of suppression of any side reaction.

When the polymerization is carried out at a liquid temperature lowerthan 25° C., the production of a byproduct such as an oligomer by theprogress of a side reaction is suppressed to improve the conductivity ofthe obtained polymer. In addition, a decrease of conductivity due tochange of oxidized and reduced structures of main chain can besuppressed.

In the present invention, the phrase “polymerization is carried out at aliquid temperature lower than 25° C.” means that the maximum temperatureof the reaction solution in the polymerization step (Z1) is lower than25° C.

The upper limit of liquid temperature (i.e., temperature of the reactionsolution) in polymerization is preferably 14° C. or lower, morepreferably lower than 10° C., and further preferably lower than 5° C. Onthe other hand, the lower limit of liquid temperature is notparticularly limited. However, the lower limit of liquid temperature ispreferably −15° C. or higher, more preferably −10° C. or higher, andfurther preferably −5° C. or higher since a sufficient reaction rate canbe maintained and the reaction time can be shortened.

When a mixed solution of an aniline derivative (A) and a basic compound(B) is added dropwise, the liquid temperature in the polymerization canbe controlled by adjusting the addition rate. On the other hand, when anoxidizing agent (D) solution is added dropwise, the liquid temperaturein the polymerization can be controlled by adjusting the addition rate,the flow rate and temperature of a refrigerant which cools a reactor.

In the polymerization step (Z1), the liquid temperature at the start ofpolymerization reaction is preferably lower than 5° C., more preferably3° C. or lower, further preferably 0° C. or lower, particularlypreferably −3° C. or lower, and most preferably −5° C. or lower. As theliquid temperature at the start of polymerization reaction is lower,decrease of conductivity due to the progress of a side reaction andchange of oxidized and reduced structures of main chain can besuppressed.

The lower limit of liquid temperature at the start of polymerizationreaction is not particularly limited. However, the lower limit of liquidtemperature is preferably −50° C. or higher, more preferably −40° C. orhigher, and further preferably −30° C. or higher since a sufficientreaction rate can be maintained and the reaction time can be shortened.

In the method for adding dropwise a mixed solution of an anilinederivative (A) and a basic compound (B) to an oxidizing agent (D)solution, the liquid temperature at the start of polymerization reactionin the present invention refers to a temperature of the oxidizing agent(D) solution just before dropwise addition of the mixed solution. In themethod for adding dropwise an oxidizing agent (D) solution to a mixedsolution of an aniline derivative (A) and a basic compound (B), theliquid temperature at the start of polymerization reaction refers to atemperature of the mixed solution just before dropwise addition of theoxidizing agent (D) solution.

The difference between the maximum temperature (lower than 25° C.) ofthe liquid temperature in the polymerization and the temperature at thestart of polymerization reaction is preferably lower than 50° C., morepreferably lower than 30° C., and further preferably lower than 15° C.As the temperature difference is smaller, the production of a byproductdue to the progress of a side reaction can be suppressed.

In the polymerization step (Z1), the pH in a reaction system during thepolymerization is preferably adjusted to 7 or less, and more preferablyto 6 or less.

When the pH in the reaction system is 7 or less, the side reaction isunlikely to proceed, and the production of a low molecular masssubstance such as a monomer, an oligomer, and impurities is suppressed.As a result, the conductivity and purity of the obtained polymer areimproved.

The pH in the reaction system during the polymerization can becontrolled by addition of protonic acid.

Examples of protonic acid include mineral acids such as hydrochloricacid, nitric acid, sulfuric acid, and borofluoric acid; superstrongacids such as trifluoromethanesulfonic acid; organic sulfonic acids suchas methansulfonic acid, dodecylbenzenesulfonic acid, toluenesulfonicacid, and camphorsulfonic acid; and high molecular acids such aspolystyrenesulfonic acid, polyacrylic acid, polyvinylsulfonic acid, andpoly-2-acrylamido-2-methylpropanesulfonic acid. Among them, from theviewpoint of handleability, for example, hydrochloric acid, nitric acid,sulfuric acid, and p-toluenesulfonic acid are preferable.

The amount of protonic acid to be added is not particularly limited aslong as an oxidizing agent is not precipitated. Specifically, the amountof protonic acid to be added preferably satisfies a molar ratio of theprotonic acid to the oxidizing agent of 0.01:100 to 50:100, and morepreferably 0.01:100 to 45:100. When the amount of protonic acid to beadded falls within the above-described range, the precipitation of amonomer is suppressed, and the progress of the reaction is unlikely tobe inhibited. Therefore, the production of a low molecular masssubstance such as a monomer, an oligomer, and impurities is suppressed.As a result, the conductivity and purity of the obtained polymer areimproved.

In the polymerization step (Z1), after a mixed solution of an anilinederivative (A) and a basic compound (B) and an oxidizing agent (D)solution are mixed (when one solution is added dropwise to the othersolution to perform polymerization, after dropwise addition), thereaction solution is preferably held at a temperature lower than 25° C.When the reaction solution is held at a temperature lower than 25° C., ahigh molecular mass polymer is easily obtained.

From the viewpoint of easy production of a high molecular mass polymerand suppression of a side reaction, the retention temperature of thereaction solution is preferably lower than 20° C., more preferably 15°C. or lower, further preferably 10° C. or lower, particularly preferably5° C. or lower, and most preferably 0° C. or lower.

Further, the retention temperature of the reaction solution ispreferably uniform.

The retention time of the reaction solution is preferably 0.5 to 12hours. From the viewpoint of conductivity and industrial availability,the retention time of the reaction solution is more preferably about 1to about 12 hours, and further preferably 4 to 12 hours.

A method for controlling the retention temperature of a reactionsolution is not particularly limited. In the method, for example, theretention time of a reaction solution can be controlled by adjusting theflow rate and temperature of a refrigerant which cools a reactor. Such amethod is selected each time according to a reactor. From the viewpointof industrial availability, it is preferable that the temperature of therefrigerant be adjusted.

A stirring procedure may be used in combination if needed to uniformlykeep the retention temperature of the reaction solution.

The conductive aniline polymer obtained in the polymerization step (Z1)may be obtained in a state of a polymer solution in which the polymer isdissolved in a solvent (C) or a polymer dispersion in which the polymeris dispersed in a solvent (C).

From the obtained conductive aniline polymer, the solvent (C) isremoved, and the polymer may be then used for various applications as itis. However, the polymer solution or the polymer dispersion may containan unreacted monomer, an oligomer, and impurities. Therefore, it ispreferable that the obtained conductive aniline polymer be purified andthen used. The polymer is purified to remove a low molecular masssubstance such as a monomer, an oligomer, and impurities, and then aconductive aniline polymer having higher purity and higher conductivityis obtained.

Examples of a method for purifying a polymer include a membranefiltration method, a precipitation purification method, and a cationicexchange method. Among them, from the viewpoint of excellentpurification efficiency, a membrane filtration method and aprecipitation purification method are preferable.

Hereinafter, the membrane filtration step and the precipitationpurification step will be specifically described. A conductive anilinepolymer before purification is also referred to as an “unpurifiedconductive polymer.”

Membrane Filtration Step

The membrane filtration step is a step of purifying a solutioncontaining a product obtained in the polymerization step (Z1) bymembrane filtration.

In the membrane filtration step, a product (unpurified conductivepolymer) is separated from the reaction solution in the polymerizationstep (Z1). A separation method is not particularly limited, and examplesthereof include filtration under reduced pressure, filtration underpressure, centrifugation, and centrifugal filtration. In particular,when a separation device for centrifugal separation is used, a producthaving high purity tends to be obtained.

Further, when a product is separated from the reaction solution, anyunreacted monomer, an oligomer, and impurities in a solid may be washedoff. Examples of washing liquid include alcohols, acetone, acetonitrile,N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

The product thus separated is dissolved in a solvent to give a solution(polymer solution). Then, the polymer solution is filtered through amembrane. Examples of a solvent used in the membrane filtration includewater, water containing a basic salt, water containing an acid, watercontaining alcohol, and a mixture thereof.

However, when the unpurified conductive polymer obtained in thepolymerization step (Z1) is dissolved in a solvent (C), a polymersolution in which the product is not separated may be subjected tomembrane separation as it is.

The separation membrane used in the membrane filtration is preferably anultrafiltration membrane in view of removal efficiency of an unreactedmonomer, an oligomer, and impurities.

An organic membrane using a polymer such as cellulose, celluloseacetate, polysulfone, polypropylene, polyester, polyether sulfone, andpolyvinylidene fluoride as a material for the separation membrane and aninorganic membrane using an inorganic material such as ceramics as thematerial for the separation membrane can be used. The material for theseparation membrane is not particularly limited as long as it is usuallyused for a material for an ultrafiltration membrane.

From the viewpoint of removal of impurities, an ultrafiltration membranepreferably has a molecular mass cutoff of 1,000 to 100,000, morepreferably 5,000 to 50,000, further preferably 10,000 to 50,000, andparticularly preferably 10,000 to 30,000.

As the molecular mass cutoff of an ultrafiltration membrane is larger,the critical flux becomes higher. As a result, the removal rate of anunreacted monomer, an oligomer, and the like is increased. At the sametime, the conductivity of the polymer obtained after purification tendsto be higher, and the yield thereof tends to be lowered.

Examples of a process of membrane filtration include a cross flowprocess and a process of filtration under pressure. However, in view ofproductivity, a continuous cross flow process is preferable. In thecontinuous cross flow process, a solution is allowed to flow along aseparation membrane, and a part of the solution penetrates theseparation membrane to be purified.

Further, in the cross flow process, a polymer solution can becontinuously contacted with the separation membrane many times.Therefore, the purification degree can be increased. The solvent in thepolymer solution penetrates the separation membrane. For this reason,the polymer solution is concentrated in the purification, and theviscosity is increased. Therefore, an operational problem may occur. Inthis case, a solvent is properly supplied to dilute the polymer solutionto an appropriate concentration. Thus, purification treatment can becontinued.

When membrane filtration is carried out by the cross flow process, thefiltration pressure depends on an ultrafiltration membrane or afiltration device. In view of productivity, the filtration pressure ispreferably about 0.01 to 1.0 MPa, and more preferably 0.01 to 0.5 MPa.

On the other hand, when membrane filtration is carried out by theprocess of filtration under pressure, the filtration pressure ispreferably 0.01 to 0.35 MPa.

The filtration time is not particularly limited. However, when themolecular mass distribution is evaluated by Gel PermeationChromatography (GPC), the filtration time is preferably a time elapseduntil the peak of a low molecular mass substance such as an unreactedmonomer, an oligomer, and impurities, which have a molecular mass equalto or less than the molecular mass cutoff do not appear.

The filtration time may be determined by a process other than theprocess using GPC. For example, such a process may include filtering aconcentrated liquid sampled every constant time by a simpleultrafiltration kit, and measuring a solid content of a filtrate (and aconcentrated liquid which remains on the membrane) to determine thefiltration time.

Further, it is preferable that the filtration time be a time whenmembrane filtration is continued until the surface resistivity of acoating film formed of a conductive aniline polymer is 10⁶ Ω/square orless, more preferably 10⁵ Ω/square or less, and further preferably 10⁴Ω/square or less.

The longer the filtration time is under the same condition other thanthe time, the higher the purification degree is. As a result, theconductivity of the conductive aniline polymer obtained afterpurification tends to be higher.

When an aniline derivative (A) is polymerized in the presence of a basiccompound (B), as described above, an acidic group in the unpurifiedconductive polymer obtained in the polymerization step (Z1) is reactedwith the basic compound (B) to form a salt.

Specifically, when an aniline derivative (A) is polymerized in thepresence of sodium hydroxide in the polymerization step (Z1), most ofthe acidic groups in the isolated polymer react to form sodium salts.Similarly, when an aniline derivative (A) is polymerized in the presenceof ammonia, almost all the acidic groups react to form ammonium salts.When an aniline derivative (A) is polymerized in the presence oftrimethylamine, almost all the acidic groups react to form trimethylammonium salts. When an aniline derivative (A) is polymerized in thepresence of quinoline, almost all the acidic groups react to formquinolinium salts.

A polymer having a salt group formed from a part or all of the acidicgroups, as described above, may has lower conductivity, as compared witha polymer not having a salt.

A basic compound (B) is almost removed with a low molecular masssubstance such as an unreacted monomer, an oligomer, and impurities whenthe unpurified conductive polymer is purified. Alternatively, in orderto further remove the basic compound (B), a demineralization treatmentmay be carried out before or after the membrane filtration step(demineralization step).

When the demineralization step is carried out after the membranefiltration step, a sample liquid after the purification step may be usedas it is.

Examples of a demineralization treatment method include an ion exchangemethod. Specific examples thereof include an ion exchange method using acation exchange resin, an electrodialysis method, and a treatment methodusing an acid-containing solution. Among them, an ion exchange methodusing a cation exchange resin and an electrodialysis method arepreferable. In particular, an electrodialysis method is preferable sincethe step is simple and a running cost is low.

In the ion exchange method using a cation exchange resin, the amount ofa sample solution, for example, a 5% polymer aqueous solution, ispreferably an amount corresponding to up to 5-fold volume, and morepreferably an amount corresponding to up to 10-fold volume, relative tothat of the cation exchange resin.

Examples of the cation exchange resin include “Diaion SK1B” availablefrom Mitsubishi Chemical Corporation, “Amberlite IR-120H” available fromOrgano Corporation., and “DOWEX 50W” available from Dow ChemicalCompany.

On the other hand, in the electrodialysis method, an ion exchangemembrane used is not particularly limited. However, in order to suppresspenetration due to diffusion of impurities, it is preferable that theion exchange membrane be subjected to monovalent ion selectivepermeation treatment, and have a molecular mass cutoff of 300 or less.As such an ion exchange membrane, “Neosepta CMK (cation exchangemembrane, molecular mass cutoff: 300)” or “Neosepta AMX (anion exchangemembrane, molecular mass cutoff: 300),” available from AstomCorporation, is suitably used.

As the ion exchange membrane used in the electrodialysis method, abipolar membrane may be used. The bipolar membrane is an ion exchangemembrane having a structure in which an anion exchange layer and acation exchange layer are bonded together. As such a bipolar membrane,for example, “PB-1E/CMB” available from Astom Corporation is suitablyused.

The current density in electrodialysis is preferably equal to or lessthan the limiting current density. The applied voltage across thebipolar membrane is preferably 10 to 50 V, and more preferably 25 to 35V.

The basic compound (B) can be effectively removed from the conductiveaniline polymer (A) by demineralization treatment, to improve theconductivity of the conductive aniline polymer.

The conductive aniline polymer after the purification step anddemineralization treatment is a state in which the polymer is dissolvedin a solvent such as water. Therefore, a solid conductive anilinepolymer can be obtained by removing the solvent through lyophilizationor the like. Alternatively, a conductive aniline polymer dissolved inthe solvent may be used as a conductive aniline polymer solution as itis.

Precipitation Purification Step

The precipitation purification step is a step of purifying a solutioncontaining a product obtained in the polymerization step (Z1) byprecipitation.

Examples of a method of precipitation purification include a method inwhich a poor solvent is added to the polymer solution to obtain apurified polymer as a precipitated product, and a method in which apolymer solution dissolved in a good solvent is gradually added to apoor solvent to obtain a purified polymer as a precipitated product.

In the precipitation purification step, a product (unpurified conductivepolymer) is first separated from the reaction solution of thepolymerization step (Z1). The separation method is not especiallylimited, and may be the separation method exemplified in the descriptionof membrane filtration step.

Further, when the product is separated from the reaction solution, anunreacted monomer, an oligomer, and impurities in a solid may be washedoff. Examples of the washing liquid include those exemplified in thedescription of membrane filtration step.

The product thus separated is dissolved in a good solvent to give asolution (polymer solution). Then, the polymer solution is purified byprecipitation.

Examples of a good solvent used in the precipitation purificationinclude solvents such as water, water containing a basic salt, watercontaining an acid, and water containing alcohol, and a mixture thereof.From the viewpoint of solubility of a product, water containing a basicsalt and water containing an acid are preferable.

The higher the temperature difference between a good solvent and a poorsolvent is, the larger the amount of the resultant precipitate is.Therefore, it is preferable that a product be dissolved in a goodsolvent at a temperature equal to or lower than the temperature at whichthe good solvent boils to enhance the solubility and a poor solvent at atemperature higher than a freezing temperature be mixed in the polymersolution to increase the amount of a precipitate.

The concentration of a polymer solution is not particularly limited aslong as it falls within a range in which the product is dissolved in agood solvent. From the viewpoint of removal of impurities, theconcentration of a polymer solution is preferably 1 to 50% by mass, andmore preferably 3 to 30% by mass.

Alternatively, when the unpurified conductive polymer obtained in thepolymerization step (Z1) is dissolved in a solvent (C), a polymersolution in which a product is not separated may be subjected toprecipitation purification as it is.

On the other hand, examples of the poor solvent include one having asolubility parameter (SP value) of about 20 to 40 MPa^(1/2). By usingalcohols, acetone, acetonitrile, N,N-dimethylformamide, formamide,glycerol, N-methylpyrrolidinone, or dimethylsulfoxide as a poor solvent,a polymer having a high purity can be obtained.

The SP value of an organic solvent can be calculated in accordance withthe method described in “Polymer Handbook,” Fourth Edition, pp. VII-675to VII-711. Specifically, the method is described in Table 1 (p.VII-683) and Tables 7 and 8 (pp. VII-688 to VII-711).

The amount of a poor solvent to be added relative to the polymersolution dissolved in the good solvent depends on the SP value of thesolvent. For example, when a solvent having a SP value of about 20 to 25MPa^(1/2) is used as a poor solvent, the ratio of the amount of thepolymer solution dissolved in the good solvent to the amount of the poorsolvent is preferably 1:0.1 to 1:5 (by mass), and particularlypreferably 1:0.7 to 1:2 (by mass) from the viewpoint of removal ofimpurities.

For example, when a solvent having a SP value of about 25 to 40MPa^(1/2) is used as a poor solvent, the ratio of the amount of thepolymer solution dissolved in the good solvent to the amount of the poorsolvent is preferably 1:2 to 1:20 (by mass), and particularly preferably1:3 to 1:17 (by mass) from the viewpoint of removal of impurities.

When the amount of a poor solvent to be added falls within theabove-described range, the proportion of a low molecular mass substancesuch as an unreacted monomer, an oligomer, and impurities contained inthe precipitate is reduced. As a result, the purity of the obtainedpolymer is improved.

When the proportion of the poor solvent is small, the amount of aprecipitated polymer is small. On the other hand, when the proportion ofthe poor solvent is large, the amount of a low molecular mass substancein the precipitate is increased.

The precipitated polymer is separated by filtration. However, a part ofthe low molecular mass substance such as an unreacted monomer, anoligomer, and impurities are dissolved in the filtrate. Examples of aseparation device used in this case include devices for filtration underreduced pressure, filtration under pressure, centrifugation, andcentrifugal filtration. In particular, when a separation device forcentrifugal separation is used, a product having high purity tends to beobtained. Therefore, this is preferable.

Further, the polymer separated by filtration may be purified byrepetitive precipitation. The larger the number of precipitationpurification is, the higher the degree of purification is. Therefore,the conductivity of the aniline polymer obtained after purificationtends to be enhanced.

The polymer (purified polymer) thus purified by precipitation ispreferably purified by further membrane filtration. Specifically, asolution containing the purified polymer is preferably subjected tomembrane filtration. A method of membrane filtration is the same as themethod exemplified in the description of the membrane filtration step.Further, demineralization may be carried out before or after themembrane filtration step.

The conductive aniline polymer thus obtained has an area ratio (X/Y) of1.20 or more, which is calculated by the evaluation process includingthe steps (I) to (VI), and therefore has excellent conductivity.

In particular, when the membrane filtration step and the precipitationpurification step are carried out after the polymerization step (Z1), anunreacted monomer, an oligomer, impurities and the like are sufficientlyremoved. Thus, a conductive aniline polymer having high purity and ahigh molecular mass can be obtained. Therefore, the conductivity isimproved.

Further, as the conductive aniline polymer thus obtained can bedissolved in a solvent such as only water, water containing a base and abasic salt, water containing an acid, methanol, ethanol, or 2-propanol,or a mixture thereof, the workability is excellent. Specifically, 0.1 gor more of the conductive aniline polymer is uniformly dissolved in 10 gof the solvent (liquid temperature: 25° C.).

As described above, according to the method for producing a conductiveaniline polymer of the present invention, a conductive aniline polymerhaving high conductivity can be mass-produced from inexpensive rawmaterials by chemical oxidation polymerization.

In addition, according to the present invention, the molecular mass of apolymer can be increased, and a conductive aniline polymer havingexcellent thermal resistance can be obtained.

Second Embodiment

In the embodiment, a polymerization step (Z2) shown below is used as thepolymerization step (Z).

A method for producing a conductive aniline polymer (P) of theembodiment includes a polymerization step (Z2) of adding an anilinederivative (A) represented by the formula (2) and an oxidizing agent (D)to a solution in which a conductive aniline polymer (P-1) having arepeating unit represented by the formula (1) is dissolved in a solvent(C) or a dispersion in which the conductive aniline polymer (P-1) isdispersed in a solvent (C) to polymerize the aniline derivative.

In the polymerization step (Z2), a basic compound (B) may be furtheradded to a solution or a dispersion of the conductive aniline polymer(P-1) to polymerize the aniline derivative, if necessary.

Conductive Aniline Polymer (P-1)

A conductive aniline polymer (P-1) used in the polymerization step (Z2)of the embodiment has a repeating unit represented by the formula (1).

The conductive aniline polymer (P-1) is produced by chemical oxidationpolymerization of an aniline derivative (A) represented by the formula(2) by using an oxidizing agent (D) in a solution containing a basiccompound (B). For example, the conductive aniline polymer (P-1) can beproduced by a method described in JP-A-7-196791.

Specific examples of a method for producing the conductive anilinepolymer (P-1) include a method for adding dropwise a mixed solution inwhich an aniline derivative (A) and a basic compound (B) are dissolvedin a solvent to an oxidizing agent solution in which an oxidizing agent(D) is dissolved in a solvent; a method for adding dropwise an oxidizingagent solution to a mixed solution of an aniline derivative (A) and abasic compound (B); a method for adding dropwise a mixed solution of ananiline derivative (A) and a basic compound (B) and an oxidizing agentsolution to a reaction vessel at the same time; and a method forcontinuously supplying an oxidizing agent solution and a mixed solutionof an aniline derivative (A) and a basic compound (B) and pushing offthem to polymerize the aniline derivative.

It is preferable that a mixed solution of an aniline derivative (A) anda basic compound (B) be mixed in an oxidizing agent solution and then areaction solution be held as it is. The retention temperature ispreferably 20° C. or lower, and the retention time is preferably 0.5 to12 hours.

In the embodiment, a step of obtaining a conductive aniline polymer(P-1) is also referred to as “polymerization step (Z_(pre)).”

Examples of an aniline derivative (A), a basic compound (B), and anoxidizing agent (D), used in the production of a conductive anilinepolymer (P-1) include those exemplified as the aniline derivative (A),basic compound (B), and oxidizing agent (D), respectively, in the firstembodiment.

Further, when a conductive aniline polymer (P-1) is produced, thesolvent (C) exemplified in the first embodiment can be used.

From the viewpoint of conductivity of the obtained conductive anilinepolymer (P-1), the temperature of a reaction solution is preferably 25°C. or lower, more preferably 10° C. or lower, and further preferably 0°C. or lower.

The resulting conductive aniline polymer (P-1) may be purified bymembrane filtration or the like before the polymerization step (Z2)described below. Examples of a membrane filtration method include themethods described in the first embodiment.

Aniline Derivative (A)

An aniline derivative (A) used in the polymerization step (Z2) of theembodiment is a compound represented by the formula (2). Specificexamples of the aniline derivative (A) include aniline derivatives (A)described in the first embodiment.

The type of the aniline derivative (A) used in the production of aconductive aniline polymer (P-1) and the type of the aniline derivative(A) used in the polymerization step (Z2) may be the same or different.However, the types are preferably the same.

Basic Compound (B)

Examples of a basic compound (B) used in the polymerization step (Z2) ofthe embodiment include the basic compounds (B) described in the firstembodiment.

The type of the basic compound (B) used in the production of aconductive aniline polymer (P-1) and the type of the basic compound (B)used in the polymerization step (Z2) may be the same or different.However, the types are preferably the same.

For example, when the basic compound (B) is used as a solution, theconcentration thereof is preferably 0.1 mol/L or more, more preferably0.1 to 10.0 mol/L, and further preferably 0.2 to 8.0 mol/L. When theconcentration of the basic compound (B) is 0.1 mol/L or more, a polymercan be obtained in a high yield. On the other hand, when theconcentration of the basic compound (B) is 10.0 mol/L or less, theconductivity of the obtained polymer tends to be enhanced.

The mass ratio of the aniline derivative (A) to the basic compound (B)is preferably 1:100 to 100:1, and more preferably 10:90 to 90:10 fromthe viewpoint of conductivity.

When the proportion of the basic compound (B) is low, the solubility ina solvent is lowered, and the reactivity is also lowered. As a result,the conductivity of the obtained polymer may be lowered. In contrast,when the proportion of the basic compound (B) is high, a salt is moreeasily formed from an acidic group in the obtained polymer and the basiccompound (B). Thus, the conductivity of the polymer may be lowered.

Therefore, when the proportion of the basic compound (B) falls withinthe preferable range, the solubility in a solvent and the reactivity ofthe basic compound (B) are enhanced, and the conductivity of theobtained polymer is improved.

Solvent (C)

Examples of a solvent (C) used in the polymerization step (Z2) of theembodiment include the solvents (C) described in the first embodiment.

The type of the solvent (C) used in the production of the conductiveaniline polymer (P-1) and the type of the solvent (C) used in thepolymerization step (Z2) may be the same or different. However, thetypes are preferably the same.

As the solvent (C), water alone is preferably used. However, when amixed solvent of water and a water-soluble organic solvent is used, thecontent of water in the solvent (C) is preferably 35% by volume or more,and more preferably 40% by mass or more, relative to the entire volumeof the solvent (C). When the content of water in the solvent (C) is 35%by volume or more, the precipitation of the aniline derivative (A) andan oxidizing agent described below can be suppressed. Therefore, thepolymerization reaction of the aniline derivative (A) proceedssufficiently, and a conductive aniline polymer (P) having a highermolecular mass is easier to be produced.

Oxidizing Agent (D)

Examples of an oxidizing agent (D) used in the polymerization step (Z2)of the embodiment include the oxidizing agents (D) described in thefirst embodiment.

The type of the oxidizing agent (D) used in the production of theconductive aniline polymer (P-1) and the type of the oxidizing agent (D)used in the polymerization step (Z2) may be the same or different.However, the types are preferably the same.

In addition, it is effective that a transition metal compound such asiron and copper is used as a catalyst together with the oxidizing agent.

The amount of the oxidizing agent (D) to be used is preferably 1 to 5mol, and more preferably 1 to 3 mol, relative to 1 mol of the anilinederivative (A). When the amount of the oxidizing agent (D) to be usedfalls within the above-described range, the molecular mass of a polymercan be sufficiently increased and the main chain can be sufficientlyoxidized.

From the viewpoint of reactivity, it is preferable that polymerizationbe carried out in a system where the molar amount of the oxidizing agent(D) is equal to or more than the molar amount of the aniline derivative(A). When the molar amount of the oxidizing agent (D) is less than theequimolar amount, a lot of unreacted substances tend to remain after thepolymerization reaction. When the molar amount of the oxidizing agent(D) is more than the equimolar amount, a lot of byproducts tend to beproduced.

Polymerization Step (Z2)

The polymerization step (Z2) of the embodiment is a step of adding theaniline derivative (A) and the oxidizing agent (D) to a solution inwhich the conductive aniline polymer (P-1) is dissolved in the solvent(C) or a dispersion in which the conductive aniline polymer (P-1) isdispersed in the solvent (C) to polymerize the aniline derivative.

Specific examples of polymerization method include a method for addingdropwise an aniline derivative solution in which the aniline derivative(A) is dissolved in the solvent and an oxidizing agent solution in whichthe oxidizing agent (D) is dissolved in the solvent to a solution or adispersion of the conductive aniline polymer (P-1) at the same time; amethod for adding dropwise a mixed solution in which the anilinederivative (A) and the basic compound (B) are dissolved in the solventand an oxidizing agent solution to a solution or a dispersion of theconductive aniline polymer (P-1) at the same time; and a method forcontinuously supplying a solution or dispersion of the conductiveaniline polymer (P-1), an aniline derivative solution or a mixedsolution of the aniline derivative solution and the basic compound (B)and an oxidizing agent solution to a reactor and pushing off them toperform polymerization. Among the methods, from the viewpoint ofsuppression of side reaction, a preferable method is a method for addingdropwise a solution of the aniline derivative or a mixed solution of thesolution and the basic compound (B) and an oxidizing agent solution to asolution or a dispersion of the conductive aniline polymer (P-1) at thesame time.

The solution of the conductive aniline polymer (P-1) or the dispersionof the conductive aniline polymer (P-1) can be obtained by dissolving ordispersing the conductive aniline polymer (P-1) in the solvent (C).

When the solvent (C) is used in the production of the conductive anilinepolymer (P-1), the conductive aniline polymer (P-1) is obtained in astate of a solution (polymer solution) in which the polymer is dissolvedin the solvent (C) or a dispersion (polymer dispersion) in which thepolymer is dispersed in the solvent (C). Therefore, the solution ordispersion may be used in the polymerization step (Z2) as it is.Alternatively, the solution or dispersion is added to the solvent (C),and diluted, and then the diluted solution may be used in thepolymerization step (Z2).

Further, an aniline derivative solution can be obtained by dissolvingthe aniline derivative (A) in the solvent (C). The aniline derivativesolution is preferably prepared so that the amount of an anilinederivative (A) to be provided is 5 to 200 parts by mass relative to 100parts by mass of the solvent (C). When a mixed solution of the anilinederivative (A) and the basic compound (B) is prepared, the mass ratio ofthe aniline derivative (A) to the basic compound (B) preferably fallswithin the above-described range.

The oxidizing agent solution can be obtained by dissolving the oxidizingagent (D) in the solvent (C). The oxidizing agent solution is preferablyprepared so that the amount of an oxidizing agent to be provided is 5 to200 parts by mass relative to 100 parts by mass of the solvent (C).

However, the solubility in the solvent (C) depends on types of theaniline derivative (A) and the oxidizing agent (D) to be used.Therefore, the amount of the aniline derivative (A) to be provided andthat of the oxidizing agent (D) to be provided need to be adjusted ineach case.

It is preferable that the solvent (C) used in the aniline derivativesolution, the mixed solution, and the oxidizing agent solution be of thesame type as that of the solvent used for the solution or dispersion ofthe conductive aniline polymer (P-1).

The amount of the aniline derivative solution, the mixed solution of ananiline derivative and a basic compound (B), or the oxidizing agentsolution, to be added (hereinafter, which are collectively referred toas “addition liquid”) may be adjusted according to the concentrationsthereof, and the size and heat removal performance of a reactor.

The stage of initiating the polymerization step (Z2) is preferably set0.5 hour or later after completion of production step of the conductiveaniline polymer (P-1).

The dropping time of addition liquid depends on the amount of additionliquid to be added. In view of reaction rate of growth of polymer, thedropping time is preferably a time proper for each case. From theviewpoint of industrial availability, the dropping time is preferably 5minutes to 24 hours.

As described above, an aniline derivative (A) and an oxidizing agent (D)are added to a solution or a dispersion of the conductive anilinepolymer (P-1) to further promote the polymerization reaction (that is,to perform additional polymerization). As a result, a conductive anilinepolymer (P) having a higher molecular mass and higher conductivity canbe obtained.

In the polymerization step (Z2), the temperature of the reactionsolution is preferably 25° C. or lower, more preferably 10° C. or lower,and further preferably 0° C. or lower. The conductivity of the obtainedpolymer is enhanced when the temperature of the reaction solution is 25°C. or lower.

In the polymerization step (Z2), the pH in a reaction system during thepolymerization is preferably adjusted to 7 or less, and more preferablyto 6 or less.

When the pH in the reaction system is 7 or less, the side reaction isunlikely to proceed, and the production of a low molecular masssubstance such as a monomer, an oligomer, and impurities is suppressed.As a result, the conductivity and purity of the obtained polymer areimproved.

The pH in the reaction system during the polymerization can becontrolled by addition of protonic acid.

Examples of protonic acid include the protonic acid shown in thedescription of the first embodiment.

The amount of protonic acid to be added is not particularly limited aslong as an oxidizing agent is not precipitated. Specifically, the amountof protonic acid to be added preferably satisfies a molar ratio of theprotonic acid to the oxidizing agent of 0.01:100 to 50:100, and morepreferably 0.01:100 to 45:100. When the amount of protonic acid to beadded falls within the above-described range, the precipitation of amonomer is suppressed, and the progress of the reaction is hardlyinhibited. Therefore, the production of a low molecular mass substancesuch as a monomer, an oligomer, and impurities is suppressed. As aresult, the conductivity and purity of the obtained polymer areimproved.

In the polymerization step (Z2), after an aniline derivative (A) and anoxidizing agent (D) are added to a solution or a dispersion of theconductive aniline polymer (P-1), the reaction solution is preferablyheld at 20° C. or lower. When the reaction solution is held at 20° C. orlower, a high molecular mass polymer is easily obtained.

From the viewpoint of easy production of high molecular mass polymer andsuppression of a side reaction, the retention temperature of thereaction solution is preferably 15° C. or lower, further preferably 5°C. or lower, and particularly preferably 0° C. or lower.

Further, the retention temperature of the reaction solution ispreferably uniform.

The retention time of the reaction solution is preferably 0.5 to 12hours. From the viewpoint of conductivity and industrial availability,the retention time of the reaction solution is more preferably about 1to about 12 hours, and further preferably 4 to 12 hours.

A method for controlling the retention temperature of the reactionsolution is not particularly limited. For example, the retention time ofthe reaction solution can be controlled by adjusting the flow rate andtemperature of the refrigerant which cools a reactor. The method isselected according to a reactor. From the viewpoint of industrialavailability, it is preferable that the temperature of the refrigerantbe adjusted.

A stirring procedure may be used in combination if needed to uniformlykeep the retention temperature of the reaction solution.

The number of the polymerization step (Z2) may be one. Alternatively, ananiline derivative (A) and an oxidizing agent (D) are further added tothe reaction mixture, and a plurality of polymerization steps (Z2) maybe carried out. The number of the polymerization step (Z2) depends onthe size and heat removal performance of a reactor. However, by aplurality of polymerization steps (Z2), a conductive aniline polymer (P)having a higher molecular mass can be obtained.

A plurality of polymerization steps (Z2) may cause problems such as anincreased volume of reaction solution. In such a case, a part of thereaction solution is taken out, and an aniline derivative (A) and anoxidizing agent (D may be added to the obtained reaction solution toperform an additional polymerization step (Z2). In all thepolymerization steps (Z2), the reaction solution need not be held at 20°C. or lower. However, from the viewpoint of adjustment of temperature ofthe reaction solution, the reaction solution in each polymerization step(Z2) is preferably held at 20° C. or lower.

The conductive aniline polymer (P) obtained by the polymerization step(Z2) is obtained in a state of a polymer solution in which the polymeris dissolved in the solvent (C) or a polymer dispersion in which thepolymer is dispersed in the solvent (C).

From the obtained conductive aniline polymer (P), the solvent (C) isremoved, and the polymer may be then used for various applications as itis. However, the polymer solution or the polymer dispersion may containan unreacted monomer, an oligomer, and impurities. Therefore, it ispreferable that the obtained conductive aniline polymer (P) be purifiedand then used. The polymer may be purified to remove a low molecularmass substance such as a monomer, an oligomer, and impurities, and thena conductive aniline polymer (P) having higher purity and higherconductivity is obtained.

In order to purify the polymer, a solution containing the productobtained in the polymerization step (Z2) may be purified by membranefiltration (membrane filtration step), or by precipitation(precipitation purification step) as described in the first embodiment.

Further, demineralization may be carried out before or after themembrane filtration step (demineralization step). The basic compound (B)can be effectively removed from the conductive aniline polymer (P) bydemineralization treatment, to increase the conductivity of theconductive aniline polymer (P).

After the precipitation purification step, the polymer (purifiedpolymer) purified by precipitation is preferably further purified bymembrane filtration (Membrane filtration step).

Examples of methods of membrane filtration, demineralization, andprecipitation purification include those described in the firstembodiment.

The conductive aniline polymer (P) thus obtained has an area ratio (X/Y)of 1.20 or more, which is calculated by the evaluation process includingthe steps (I) to (VI), and therefore has excellent conductivity.

In particular, when the membrane filtration step and the precipitationpurification step are carried out after the polymerization step (Z2), anunreacted monomer, an oligomer, impurities and the like are sufficientlyremoved. Thus, a conductive aniline polymer (P) having high purity and ahigh molecular mass can be obtained. Therefore, the conductivity isenhanced.

Further, as the conductive aniline polymer (P) thus obtained can bedissolved in a solvent such as only water, water containing a base and abasic salt, water containing an acid, methanol, ethanol, or 2-propanol,or a mixture thereof, the workability is excellent. Specifically, 0.1 gor more of the conductive aniline polymer (P) is uniformly dissolved in10 g of the solvent (liquid temperature: 25° C.).

As described above, according to the method for producing a conductiveaniline polymer of the present invention, a conductive aniline polymer(P) having high conductivity can be mass-produced from inexpensive rawmaterials by chemical oxidation polymerization.

In addition, according to the present invention, the molecular mass ofpolymer can be increased, and a conductive aniline polymer (P) havingexcellent thermal resistance can be obtained.

In further embodiments of the present invention, a polymer having ahigher molecular mass can be further produced by combination of thepolymerization steps (Z1) and (Z2).

<Application>

From the conductive aniline polymer of the present invention, aconductor can be produced by a simple procedure such as a spray coatingmethod, a dip coating method, a roll coating method, a gravure coatingmethod, a reverse coating method, a roll brushing method, an air-knifecoating method, and a curtain coating method.

Moreover, a composition containing the conductive aniline polymer as themain component can be applied to various antistatic agents, condensers,batteries, EMI shields, chemical sensors, display elements, nonlinearmolding materials, corrosion prevention, adhesives, fibers, antistaticcoating compositions, anticorrosive compositions, electrocoatingcompositions, plating primer, electrostatic coating primer, electricprevention for corrosion, and enhancement of the storing capacity ofbattery.

In particular, the conductive aniline polymer of the present inventionhas excellent conductivity and thermal resistance. Therefore, theconductive aniline polymer is suitable for applications such as acondenser in which the production process includes a heating treatmentstep.

<Method for Producing Conductive Film>

The method for producing a conductive film of the present inventionincludes applying a solution containing the conductive aniline polymerof the present invention to a base material and drying the solutionapplied to the base material.

Examples of a coating method include a spray coating method, a dipcoating method, a roll coating method, a gravure coating method, areverse coating method, a roll brushing method, an air-knife coatingmethod, and a curtain coating method.

A drying method is not particularly limited, and any known method can beemployed.

Since the conductive aniline polymer is used in the method for producinga conductive film of the present invention, a conductive film havinghigh conductivity can be produced by the simple procedure.

EXAMPLES

Hereinafter, the present invention will be described in detail byExamples. However, the present invention is not limited to the Examples.

Evaluations and measurement methods in Examples and Comparative Exampleswill be as follows.

<Evaluation and Measurement> (Calculation of Area Ratio (X/Y))

Water (ultrapure water) and methanol were mixed so that the volume ratioof water to methanol was 8:2, to prepare a mixed solvent. Sodiumcarbonate and sodium hydrogen carbonate were added to the mixed solventso that the solid content concentrations thereof were 20 mmol/L and 30mmol/L, respectively, to prepare an eluent. The resulting eluent had apH of 10.8 at 25° C.

A conductive aniline polymer was dissolved in the eluent so that thesolid content concentration was 0.1% by mass to prepare a test solution(step (I)).

The molecular mass distribution of the resulting test solution wasmeasured to obtain a chromatogram (step (II)). At this case, themolecular mass distribution was measured by a high molecular materialevaluation device (“Waters Alliance 2695, 2414 (refractive indexdetector), and 2996 (photodiode array (PDA))” manufactured by WatersCorporation) equipped with a gel permeation chromatograph connected to aPDA detector using two columns (“Tsk-Gel Alpha-M” manufactured by TosohCorporation, 7.8×300 mm), at a flow rate of 0.6 mL/min and a columntemperature of 40° C.

The retention time in the resulting chromatogram was converted to amolecular mass (M) in terms of sodium polystyrene sulfonate (step(III)). Specifically, sodium polystyrene sulfonate having each peak topmolecular mass of 206, 1,030, 4,210, 13,500, 33,500, 78,400, 158,000,and 2,350,000 was used as a standard sample. Similarly to the testsolution, each standard sample was dissolved in the eluent so that thesolid content concentration thereof was 0.05% by mass, provided that thesolid content concentration of the standard sample having a peak topmolecular mass of 206 was 25 ppm. Thus, each standard solution wasprepared. A relation between the retention time and the molecular massin each standard solution was determined by GPC, and a calibration curvewas made. From the resultant calibration curve, the retention time inthe chromatogram obtained in the step (II) was converted to a molecularmass (M) in terms of sodium polystyrene sulfonate.

Then, the area (X) of a region having a molecular mass (M) of 15,000 Daor more and the area (Y) of a region having a molecular mass (M) of lessthan 15,000 Da were each calculated (steps (IV) and (V)).

Next, the area ratio (X/Y) of the area (X) to the area (Y) wascalculated (step (VI)).

(Evaluation of Conductivity)

A conductive aniline polymer solution was applied to a glass substrateby a spin coater (“Manual Spinner ASC-4000” manufactured by Actes Inc.),and then dried by heating on a hot plate at 120° C. for 10 minutes toobtain a test piece for evaluation of conductivity. The test piece had acoating film of a predetermined thickness formed on the glass substrate.The thickness of the coating film was measured by an atomic forcemicroscope (“Nanoscale Hybrid Microscope VN-8000” manufactured byKeyence Corporation).

The surface resistivity of the resulting test piece for evaluation ofconductivity was measured by a resistivity meter (“Loresta GP”manufactured by Mitsubishi Chemical Analytech Co., Ltd.) with an in-linefour-point probe.

The volume resistivity was calculated by the product of the measuredsurface resistivity and the thickness of the coating film. Theconductivity was calculated by the reciprocal of the volume resistivity.

(Evaluation of Thermal Resistance)

A conductive aniline polymer solution was applied to a glass substrateby a spin coater (“Manual Spinner ASC-4000” manufactured by Actes Inc.),and then dried by heating on a hot plate at 160° C. for 1 hour to obtaina test piece for evaluation of conductivity. The test piece had acoating film of a predetermined thickness formed on the glass substrate.

In the same manner as in the evaluation of conductivity, the surfaceresistivity of the resulting test piece for evaluation of thermalresistance was measured and the conductivity was calculated.

Example 1-1

First, 200 mmol of ammonium peroxodisulfate and 1.0 g of sulfuric acidwere dissolved in 150 mL of a mixed solvent of water and acetonitrile(volume ratio: 1:1) cooled to 0° C. in an ethylene glycol bath at astirring power of 0.7 kw/m³ to give a solution (polymerizationinitiation temperature: reaction solution temperature, 1.5° C.). Next,to the solution, a solution of 200 mmol of 2-aminoanisole-4-sulfonicacid and 200 mmol of triethylamine in 150 mL of a mixed solvent of waterand acetonitrile (volume ratio: 1:1) was added dropwise at 200 mmol/hr.After completion of the dropwise addition, the reaction solution waskept for 2 hours under stirring at a stirring rotation speed of 200 rpmwhile the temperature of the refrigerant was adjusted so that thetemperature (retention temperature) of the reaction solution was 0° C.(polymerization step (Z1)). The maximum temperature of the reactionsolution in the polymerization step (Z1) was 8° C. when the amount ofthe added monomer was 0.75 equivalents.

The reaction product was then filtered off under cooling by a device forfiltration under reduced pressure, washed with methanol, and dried, toobtain a crude polymer.

Then, 20 g of the resulting crude polymer was dissolved in 10 L of waterto prepare a polymer solution having a solid content concentration of0.2% by mass. Subsequently, the polymer solution was concentrated to asolid content concentration of 3% by mass by an ultrafiltration unitwith a molecular mass cutoff (MWCO) of 10,000, “Vivaflow 200”manufactured by Sartorius AG (membrane filtration step). As a result, aconductive aniline polymer solution was obtained.

A part of the resultant conductive aniline polymer solution was takenout. This conductive aniline polymer solution was dissolved in theeluent prepared above so that the solid content concentration of theconductive aniline polymer in the solution was 0.1% by mass to prepare atest solution. The molecular mass (M) and area ratio (X/Y) of the testsolution were calculated. The results are shown in Table 2.

The conductivity of the conductive aniline polymer solution wasdetermined. The result is shown in Table 2.

Example 1-2

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1-1 except the followings: A solution of 200mmol of ammonium peroxodisulfate and 1.0 g of sulfuric acid in 150 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was cooledto −10° C. (polymerization initiation temperature: reaction solutiontemperature −9° C.), and the temperature of the refrigerant was adjustedso that the retention temperature after completion of the dropwiseaddition was −10° C. The results are shown in Table 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was −5° C. when the amount of the added monomer was 0.8equivalents.

Example 1-3

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1-1 except the followings: A solution of 100mmol of ammonium peroxodisulfate and 0.5 g of sulfuric acid in 75 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was cooledto −5° C. (polymerization initiation temperature: reaction solutiontemperature −3° C.). Then, a solution of 100 mmol of2-aminoanisole-4-sulfonic acid and 100 mmol of triethylamine in 75 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was addeddropwise to the former solution at 100 mmol/hr, and the temperature ofthe refrigerant was adjusted so that the retention temperature aftercompletion of the dropwise addition was −5° C. The results are shown inTable 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was −1° C. when the amount of the added monomer was 0.7equivalents.

Example 1-4

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1-1 except the followings: A solution of 200mmol of ammonium peroxodisulfate and 1.0 g of sulfuric acid in 150 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was cooledto −5° C. (polymerization initiation temperature: reaction solutiontemperature −3° C.). To this solution, a solution of 200 mmol of2-aminoanisole-4-sulfonic acid and 200 mmol of triethylamine in 150 mLof a mixed solvent of water and acetonitrile (volume ratio: 1:1) wasadded dropwise at 200 mmol/min. The results are shown in Table 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 16° C. 10 minutes after completion of the dropwiseaddition of monomer.

Example 1-5

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1 except the followings: A solution of 200mmol of 2-aminoanisole-4-sulfonic acid and 200 mmol of triethylamine in150 mL of a mixed solvent of water and acetonitrile (volume ratio: 1:1)was cooled to −5° C. in an ethylene glycol bath at a stirring power of0.7 kw/m³ (polymerization initiation temperature: reaction solutiontemperature −3° C.). To this solution, a solution of 200 mmol ofammonium peroxodisulfate and 1.0 g of sulfuric acid in 150 mL of a mixedsolvent of water and acetonitrile (volume ratio: 1:1) was added dropwiseat 200 mmol/hr. The results are shown in Table 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 1.3° C. when the amount of added ammonium peroxodisulfatesolution was 1 equivalent.

Comparative Example 1-1

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1 except the followings: A solution of 200mmol of ammonium peroxodisulfate and 1.0 g of sulfuric acid in 150 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was cooledto 2° C. (polymerization initiation temperature: reaction solutiontemperature, 3° C.). The temperature of the refrigerant was adjusted sothat the retention temperature after completion of the dropwise additionwas 25° C. The results are shown in Table 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 25° C. 45 minutes after completion of the dropwiseaddition of monomer.

Comparative Example 1-2

A test solution was subjected to measurement and evaluation after beingobtained by the polymerization step (Z1) and membrane filtration step ina manner similar to Example 1 except the followings: A solution of 200mmol of ammonium peroxodisulfate and 1.0 g of sulfuric acid in 150 mL ofa mixed solvent of water and acetonitrile (volume ratio: 1:1) was cooledto −3° C. (polymerization initiation temperature: reaction solutiontemperature −2.5° C.). To the solution, a solution of 200 mmol of2-aminoanisole-4-sulfonic acid and 200 mmol of triethylamine in 150 mLof a mixed solvent of water and acetonitrile (volume ratio: 1:1) wasadded dropwise at 400 mmol/hr. The temperature of the refrigerant wasadjusted so that the temperature (retention temperature) of the reactionsolution after completion of the dropwise addition was 25° C. Theresults are shown in Table 2.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 28° C. 15 minutes after completion of the dropwiseaddition of monomer.

TABLE 2 Maximum Reaction temperature initiation of reaction Area Filmtemperature solution Molecular ratio thickness Conductivity (° C.) (°C.) mass (M) (X/Y) (nm) (S/cm) Example 1-1 1.5 8 44690 1.72 97 8.8Example 1-2 −9 −5 51550 1.96 130 10.7 Example 1-3 −3 −1 48430 1.79 9318.3 Example 1-4 −3 16 41390 1.48 89 14.8 Example 1-5 −3 1.3 47220 1.69109 10.6 Comparative 3 25 22400 0.89 92 1.9 Example 1-1 Comparative −2.528 28680 1.19 51 3.3 Example 1-2

As shown in Table 2, each of the conductive aniline polymers of Examples1-1 to 1-5 prepared by polymerization at a liquid temperature lower than25° C. has an area ratio (X/Y) of 1.20 or more, having highconductivity. This is considered that, by carrying out thepolymerization at a temperature lower than 25° C., progress of sidereaction and change of oxidized and reduced structures of main chain canbe suppressed and therefore a high molecular mass substance can beproduced.

On the other hand, each of the conductive aniline polymers ofComparative Examples 1-1 and 1-2 polymerized at a liquid temperature of25° C. or higher has an area ratio (X/Y) of less than 1.20, having poorconductivity as compared with Examples. It is considered that when themaximum temperature of the reaction solution in the polymerization step(Z1) is 25° C. or higher, progress of side reaction and change ofoxidized and reduced structures of main chain cannot be suppressed andtherefore, a high molecular mass substance is unlikely to be obtained ascompared with Examples.

In Example 1-4 and Comparative Example 1-2, since the addition rate ofsolution of 2-aminoanisole-4-sulfonic acid and triethylamine was setfaster than those in other Examples and Comparative Example, thetemperature-rising rate of the reaction solution was faster. For thisreason, in Example 1-4, the liquid temperature of the reaction solutionafter completion of the dropwise addition was held to 0° C. However, theliquid temperature reached the maximum temperature of the reactionsolution 10 minutes after completion of the dropwise addition ofmonomer, and was 16° C. On the other hand, in Comparative Example 1-2,the liquid temperature of the reaction solution after completion of thedropwise addition was held to 25° C. However, the liquid temperaturereached the maximum temperature of the reaction solution 15 minutesafter completion of the dropwise addition of monomer, and was 28° C.

Example 2-1

First, 200 mmol of 2-aminoanisole-4-sulfonic acid and 200 mmol oftriethylamine were dissolved in 78 g of a mixed solvent of water andacetonitrile (volume ratio: 4:6) to obtain a solution of aniline havingan acidic group. Separately, a solution of 200 mmol of ammoniumpersulfate and 1.0 g of sulfuric acid in 156 g of a mixed solvent ofwater and acetonitrile (volume ratio: 4:6) was cooled in an ethyleneglycol bath at that time, the bath temperature was measured by athermocouple to be −4° C. To this solution, the solution of anilinehaving an acidic group was added dropwise at a constant rate over 1hour.

The pH in the reaction system was measured by a pH meter inserted in thereaction system. The pH at the start of dropwise addition was 0.6 andthe pH after completion of the dropwise addition was 0.6. When theamount of the added monomer was 0.3 equivalents, a maximum pH of 3.3 wasrecorded.

After completion of the dropwise addition, the bath temperature wasadjusted to −8° C., and the reaction solution was kept at thattemperature for 1 hour under stirring (polymerization step (Z1)). Fortyminutes after completion of the dropwise addition of monomer, a minimumpH of 0.6 was recorded. The maximum temperature of the reaction solutionin the polymerization step (Z1) was 9.2° C. when the amount of themonomer added at a stirring speed of 200 rpm was 0.5 equivalents.

The resulting polymer solution was then subjected to membrane filtrationby a device using a cross flow mode (membrane filtration step).“Vivaflow 200” manufactured by Sartorius AK, was used in its filtrationpart. An ultrafiltration membrane (material: polyethersulfone (PES))with a molecular mass cutoff of 10,000 Da was used as a filtrationmembrane. After completion of the membrane filtration, a solution at thefiltrated (concentrated) side was collected as a conductive anilinepolymer solution.

Subsequently, the concentration of the conductive polymer aqueoussolution was adjusted to 5%. Then, 5 g of the solution was passedthrough a column with a diameter of 1 cm, filled with 5 mL of AmberliteIR-120 B(H) (available from Organo Corporation) to perform cationicexchange (demineralization). As a result, a conductive aniline polymersolution was obtained. A part of the resulting conductive anilinepolymer solution was taken out. This was dissolved in the eluentprepared above so that the solid content concentration of the conductiveaniline polymer in the solution was 0.1% by mass to prepare a testsolution. The molecular mass (M) and area ratio (X/Y) of the testsolution were calculated. The results are shown in Table 3.

The conductivity of the conductive aniline polymer solution wasdetermined. The result is shown in Table 3.

Example 2-2

100 mmol of 2-aminoanisole-4-sulfonic acid and 100 mmol of triethylaminewere dissolved in 79.7 g of a mixed solvent of water and acetonitrile(volume ratio: 1:1) to obtain a solution of aniline having an acidicgroup. Separately, a solution of 100 mmol of ammonium persulfate and 0.5g of sulfuric acid in 39.9 g of a mixed solvent of water andacetonitrile (volume ratio: 1:1) was cooled in an ethylene glycol bathat that time, the bath temperature was measured by a thermocouple to be−4° C. To the solution, the solution of aniline having an acidic groupwas added dropwise at a constant rate over 1 hour.

The pH in the reaction system was measured by a pH meter inserted in thereaction system. The pH at the start of dropwise addition was 0.9 andthe pH after completion of the dropwise addition was 1.5. When theamount of the added monomer was 0.3 to 0.4 equivalents, a maximum pH of3.6 was recorded.

After completion of the dropwise addition, while the bath temperaturewas kept at −4° C., the reaction solution was kept at that temperaturefor 2 hour under stirring (polymerization step (Z1)). Eighty-fiveminutes after completion of the dropwise addition, a minimum pH of 0.8was recorded. The maximum temperature of the reaction solution in thepolymerization step (Z1) was 1.5° C. when the amount of the monomeradded at a stirring speed of 200 rpm was 0.6 equivalents.

Then, the slurry of the resulting reaction product was filtered off byan ultrafiltration device in the same manner as in Example 2-1 (membranefiltration step). The product was subjected to cationic exchange(demineralization). As a result, a conductive aniline polymer solutionwas obtained. Each measurement and evaluation of the obtained conductiveaniline polymer solution was carried out in the same manner as inExample 2-1. The results are shown in Table 3.

Example 2-3

First, 200 mmol of 2-aminoanisole-4-sulfonic acid and 200 mmol oftriethylamine were dissolved in 94 g of a mixed solvent of water andacetone (volume ratio: 7:3) to obtain a solution of aniline having anacidic group. Separately, a solution of 200 mmol of ammonium persulfateand 0.2 g of sulfuric acid in 187 g of a mixed solvent of water andacetone (volume ratio: 7:3) was cooled in an ethylene glycol bath atthat time, the bath temperature was measured by a thermocouple to be−3.5° C. To the solution, the solution of aniline having an acidic groupwas added dropwise at a constant rate over 1 hour.

The pH in the reaction system was measured by a pH meter inserted in thereaction system. The pH at the start of dropwise addition was 1.4 andthe pH after completion of the dropwise addition was 2.6. When theamount of the added monomer was 0.2 to 0.4 equivalents, a maximum pH of3.8 was recorded.

After completion of the dropwise addition, while the bath temperaturewas kept at −3.5° C., the reaction solution was kept at that temperaturefor 1 hour under stirring (polymerization step (Z1)). The minimum pH of1.5 was recorded 120 minutes after completion of the dropwise addition.The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 2.8° C. when the amount of the monomer added at a stirringspeed of 200 rpm was 1.0 equivalent.

The slurry of the resulting reaction product was filtered off by anultrafiltration device in the same manner as in Example 2-1 (membranefiltration step). Next, the product was subjected to cationic exchange(demineralization). As a result, a conductive aniline polymer solutionwas obtained. Each of measurement and evaluation of the obtainedconductive aniline polymer solution was carried out in the same manneras in Example 2-1. The results are shown in Table 3.

TABLE 3 Content of Maximum Molec- Film water in temperature ular Areathick- Conduc- solvent (% of reaction mass ratio ness tivity by volume)solution (° C.) (M) (X/Y) (nm) (S/cm) Exam- 40 9.2 35800 1.24 119 6.6ple 2-1 Exam- 50 1.5 50700 1.85 106 14.6 ple 2-2 Exam- 70 2.8 42000 1.58112 11.2 ple 2-3

As shown in Table 3, the area ratios (X/Y) of the conductive anilinepolymers obtained in Examples 2-1 to 2-3, in which polymerization wascarried out using a solvent (C) containing 35% by volume or more ofwater, were 1.20 or more. The conductive aniline polymers had highconductivity. It is considered that use of the solvent (C) containing35% by volume or more of water in the polymerization step (Z1)suppressed precipitation of an aniline derivative (A) and an oxidizingagent and therefore a high molecular mass substance was formed.

Example 3-1

The temperature of a refrigerant was adjusted so that the liquidtemperature in a reactor of a 250-mL round-bottom glass stirring vessel(vessel diameter: 7 cm) charged with 103 g of aqueous solution of 1mol/L ammonium peroxodisulfate and 0.005 mol of 98% by mass sulfuricacid was −5° C. To the mixture, a solution of 0.1 mol of2-aminoanisole-4-sulfonic acid in 10.1 g of 4.5 mol/L triethylamineaqueous solution was added dropwise over 1 hour. The impeller used wasan anchor impeller (impeller diameter: 5 cm) made of glass, and stirringwas carried out at the stirring rotation speed of 200 rpm. Aftercompletion of the dropwise addition, the temperature of reactionsolution was −5° C. The term “aqueous solution” means a mixed solvent inwhich water and acetonitrile are mixed in the same volumes (1:1).

After completion of the dropwise addition, while the temperature of therefrigerant was adjusted so that the temperature (retention temperature)of the reaction solution was −5° C., the reaction solution was kept atthat temperature for 2 hours under stirring at a stirring rotation speedof 200 rpm (polymerization step (Z1)). The maximum temperature of thereaction solution in the polymerization step (Z1) was 1.5° C. when theamount of the added monomer was 0.8 equivalents.

The resulting polymer solution was then subjected to membrane filtrationby a device using a cross flow mode (membrane filtration step).“Vivaflow 200” manufactured by Sartorius AK, was used in its filtrationpart. An ultrafiltration membrane (material: polyethersulfone (PES))with a molecular mass cutoff of 10,000 Da was used as a filtrationmembrane. After completion of the membrane filtration, a solution at thefiltrated (concentrated) side was collected as a conductive anilinepolymer solution.

A part of the resulting conductive aniline polymer solution was takenout. This was dissolved in the eluent prepared above so that the solidcontent concentration of the conductive aniline polymer in the solutionwas 0.1% by mass to prepare a test solution. The molecular mass (M) andarea ratio (X/Y) of the test solution were calculated. The results areshown in Table 4.

The conductivity of the conductive aniline polymer solution wasdetermined. The result is shown in Table 4.

Example 3-2

A test solution was obtained by the polymerization step (Z1) andmembrane filtration step in the same manner as in Example 3-1 exceptthat the retention time was changed into 4 hours. Each measurement andevaluation of the obtained test solution was carried out in the samemanner as in Example 3-1. The results are shown in Table 4.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 1.5° C. when the amount of the added monomer was 0.8equivalents.

Example 3-3

A test solution was obtained by the polymerization step (Z1) andmembrane filtration step in the same manner as in Example 3-1 exceptthat the retention time was changed into 6 hours. Each measurement andevaluation of the obtained test solution was carried out in the samemanner as in Example 3-1. The results are shown in Table 4.

The maximum temperature of the reaction solution in the polymerizationstep (Z1) was 1.5° C. when the amount of the added monomer was 0.8equivalents.

TABLE 4 Maxi- mum temper- Reten- ature tion Reten- of Molec- Film temp-tion reaction ular Area thick- Conduc- erature time solution mass rationess tivity (° C.) (hour) (° C.) (M) (X/Y) (nm) (S/cm) Example −5 2 1.534900 1.39 104 1.96 3-1 Example −5 4 1.5 41200 1.70 105 2.65 3-2 Example−5 6 1.5 40200 2.00 107 2.53 3-3

As shown in Table 4, the area ratios (X/Y) of the conductive anilinepolymers obtained in Examples 3-1 to 3-3, in which polymerization wascarried out at a liquid temperature lower than 25° C., were 1.20 ormore. The conductive aniline polymers had high conductivity. The longerthe retention time was, the larger the area ratio (X/Y) was. Thus, theconductivity tended to be higher.

Example 4-1

The solution of 200 mmol of 2-aminoanisole-4-sulfonic acid and 200 mmolof triethylamine dissolved in 150 mL of a mixed solvent of water andacetonitrile (volume ratio: 1:1) was added dropwise to a solution of 200mmol of ammonium peroxodisulfate dissolved in 150 mL of a mixed solventof water and acetonitrile (volume ratio: 1:1) at −5° C., at a stirringspeed of 200 mmol/hr and a stirring power of 0.7 kw/m³. After completionof the dropwise addition, while the temperature of the refrigerant wasadjusted so that the temperature (retention temperature) of the reactionsolution was 10° C., the reaction solution was kept at that temperaturefor 2 hours under stirring at a stirring rotation speed of 200 rpm(polymerization step (Z1)). The maximum temperature of the reactionsolution in the polymerization step (Z1) was 9° C. when the amount ofthe added monomer was 0.8 equivalents.

Subsequently, the resulting reaction product was filtered off by adevice for centrifugal filtration, washed with methanol, and dried, toobtain 17 g of crude polymer.

After 1 g of the resulting crude polymer was dissolved in 9 g of water(good solvent), 21 g of acetone (poor solvent) was added thereto toperform precipitation purification (precipitation purification step).

The precipitate was filtered off by a device for filtration underreduced pressure, washed with acetonitrile, and dried. Then, the polymerpurified by precipitation was dissolved in water to prepare a conductiveaniline polymer solution having a solid content concentration of 3% bymass.

A part of the resulting conductive aniline polymer solution was takenout. This was dissolved in the eluent prepared above so that the solidcontent concentration of the conductive aniline polymer in the solutionwas 0.1% by mass to prepare a test solution. The molecular mass (M) andarea ratio (X/Y) of the test solution were calculated. The results areshown in Table 5.

The conductivity of the conductive aniline polymer solution wasdetermined. The result is shown in Table 5.

Examples 4-2 and 4-3

In the same manner as in Example 4-1, a test solution was obtained bythe polymerization step (Z1) and precipitation purification step, andeach measurement and evaluation of the obtained test solution wascarried out except the followings. Thus, the amount of the good solventand the type and amount of the poor solvent were changed into thoseshown in Table 5. The results are shown in Table 5. The maximumtemperature of the reaction solution in the polymerization step (Z1) isshown in Table 5. The temperature of the reaction solution in thepolymerization step (Z1) reached the highest temperature during thedropwise addition of monomer.

TABLE 5 Poor solvent Maximum Good 2- Ace- temperature solvent Ace-Propa- Toni- of reaction Molecular Area Film Water Tone nol trilesolution mass ratio thickness Conductivity (g) (g) (g) (g) (° C.) (M)(X/Y) (nm) (S/cm) Example 9 21 — — 9 34020 1.21 96 4.2 4-1 Example 9 —21 — 9 39630 1.39 92 6.8 4-2 Example 9 — — 21 9 37170 1.37 53 5.8 4-3

As shown in Table 5, the conductive aniline polymers obtained inExamples 4-1 to 4-3, in which polymerization was carried out at a liquidtemperature lower than 25° C. and purification was carried out byreprecipitation, had an area ratio (X/Y) of 1.20 or more and also highconductivity.

When purification was carried out by reprecipitation like Examples 4-1to 4-3, a polymer having an area ratio (X/Y) of 1.20 or more, and highconductivity could be produced for a short period withoutultrafiltration.

Example 5-1 Production of Conductive Aniline Polymer (P1-2) Productionof Conductive Aniline Polymer (P1-1)

The liquid temperature in a 250-mL round-bottom glass stirring vessel(vessel diameter: 7 cm) charged with 103 g of aqueous solution of 1mol/L ammonium peroxodisulfate and 0.005 mol of 98% by mass sulfuricacid was adjusted to −5° C. To the mixture, a solution of 0.1 mol of2-aminoanisole-4-sulfonic acid dissolved in 70.3 g of 4.5 mol/Ltriethylamine aqueous solution was then added dropwise over 1 hour. Asan impeller, an anchor impeller (impeller diameter: 5 cm) made of glasswas used, and stirring was carried out at the stirring rotation speed of200 rpm. The temperature of the refrigerant was adjusted so that thetemperature of the solution in the stirring vessel before the dropwiseaddition was 10° C. The term “aqueous solution” means a mixed solvent inwhich water and acetonitrile are mixed in the same volumes (1:1).

After completion of the dropwise addition, while the temperature of therefrigerant was adjusted so that the temperature (retention temperature)of the reaction solution was 10° C., the reaction solution was kept for2 hours under stirring at a stirring rotation speed of 200 rpm(polymerization step (Z_(pre))). Thus, a conductive aniline polymer(P1-1) solution was obtained. The maximum temperature of the reactionsolution in the polymerization step was 24.8° C. when the amount of theadded monomer was 0.6 equivalents.

Production of Conductive Aniline Polymer (P1-2)

To the conductive aniline polymer (P1-1) solution (entire amount)obtained in the production of the conductive aniline polymer (P1-1),29.6 g of aqueous solution of 1 mol/L ammonium peroxodisulfate,containing 0.005 mol of 98% by mass sulfuric acid, and 0.025 mol of2-aminoanisole-4-sulfonic acid dissolved in 19.0 g of 4.5 mol/Ltriethylamine aqueous solution were each simultaneously added dropwiseover 0.5 hour (polymerization step (Z2)). Thus, a conductive anilinepolymer (P1-2) solution was obtained. In the reaction, the temperatureof the refrigerant was adjusted so that the temperature of the reactionsolution was 10° C. The maximum temperature of the reaction solution inthe polymerization step (Z2) was 11.5° C. when the amount of the addedmonomer was 0.1 equivalents.

A part of the resulting conductive aniline polymer (P1-2) solution wastaken out. This was dissolved in the eluent prepared above so that thesolid content concentration of the conductive aniline polymer in thesolution was 0.1% by mass to prepare a test solution. The molecular mass(M) and area ratio (X/Y) of the test solution were calculated. Theresults are shown in Table 6.

The conductivity of the conductive aniline polymer (P1-2) solution wasdetermined. The result is shown in Table 6. The maximum temperature ofthe reaction solution in the polymerization step (Z) is shown in Table6.

Example 5-2 Production of Conductive Aniline Polymer (P1-2′)

A conductive aniline polymer (P1-2′) was obtained by the polymerizationstep (Z2) in the same manner as in Example 5-1. Each measurement andevaluation of the obtained conductive aniline polymer (P1-2′) wascarried out except the followings. Thus, an aniline derivative (A), abasic compound (B), and an oxidizing agent (D) were added dropwise tothe conductive aniline polymer (P1-1) solution. While the temperature ofthe refrigerant was adjusted so that the temperature of the reactionsolution was 10° C., the reaction solution was kept at that temperaturefor 2 hours under stirring at a stirring rotation speed of 200 rpm. Theresults are shown in Table 6. The maximum temperature of the reactionsolution in the polymerization step (Z) is shown in Table 6.

TABLE 6 Maximum temperature Film of reaction Molecular Area thick-Conduc- Polymerization solution mass ratio ness tivity step (Z) (° C.)(M) (X/Y) (nm) (S/cm) Example (1) main reaction: 24.8 35300 1.26 97 2.315-1 production of (P1-1) (addition and retention) (2) additionalreaction: production of (P1-2) (addition) Example (1) main reaction:24.8 40800 1.41 98 2.92 5-2 production of (P1-1) (addition andretention) (2) additional reaction: production of (P1-2’) (addition andretention)

As shown in Table 6, the conductive aniline polymers (P1-2) and (P1-2′)obtained in Examples 5-1 and 5-2, in which additional polymerization wascarried out, had an area ratio (X/Y) of 1.20 or more, and thereforetheir conductivities were improved. In particular, the conductivity wasfurther enhanced in Example 5-2 where the reaction solution was kept inthe polymerization step (Z2).

Example 5-3 Production of Conductive Aniline Polymer (P2-1)

A conductive aniline polymer (P2-1) solution was obtained in the samemanner as in the production of the conductive aniline polymer (P1-1) inExample 5-1 except the followings. Thus, the temperature of therefrigerant was adjusted so that the temperature of the solution in thestirring vessel before dropwise addition was −5° C. and the temperatureof the refrigerant was adjusted so that the retention temperature of thereaction solution was −5° C. The maximum temperature of the reactionsolution in the polymerization step (Z_(pre)) is shown in Table 7.

Each measurement and evaluation of the obtained conductive anilinepolymer (P2-1) solution was carried out in the same manner as in Example5-1. The results are shown in Table 7.

Example 5-4 Production of Conductive Aniline Polymer (P2-2)

A conductive aniline polymer (P2-1) solution was obtained in the samemanner as in Example 5-3.

To the obtained conductive aniline polymer (P2-1) solution (entireamount), 29.6 g of aqueous solution of 1 mol/L ammonium peroxodisulfatecontaining 0.005 mol of 98% by mass sulfuric acid, and 0.025 mol of2-aminoanisole-4-sulfonic acid dissolved in 19.0 g of 4.5 mol/Ltriethylamine aqueous solution were each simultaneously added dropwiseover 0.5 hour (polymerization step (Z2-1)). Thus, a conductive anilinepolymer (P2-2) solution was obtained. In the reaction, the temperatureof the refrigerant was adjusted so that the temperature of the reactionsolution was −5° C. The maximum temperature of the reaction solution inthe polymerization step (Z2-1) was −4.9° C. when the amount of the addedmonomer was 0.1 equivalents.

Each measurement and evaluation of the obtained conductive anilinepolymer (P2-2) was carried out in the same manner as in Example 5-1. Theresults are shown in Table 7. The maximum temperature of the reactionsolution in the polymerization step (Z) is shown in Table 7.

Example 5-5 Production of Conductive Aniline Polymer (P2-2′)

A conductive aniline polymer (P2-2′) was obtained by the polymerizationstep (Z2-1) in the same manner as in Example 5-4 except the followings.Thus, an aniline derivative (A), a basic compound (B), and an oxidizingagent (D) were added dropwise to the conductive aniline polymer (P2-1)solution. While the temperature of the refrigerant was adjusted so thatthe temperature of the reaction solution was −5° C., the reactionsolution was then kept at that temperature for 2 hours under stirring ata stirring rotation speed of 200 rpm. Each measurement and evaluation ofthe obtained conductive aniline polymer (P2-2′) was carried out. Theresults are shown in Table 7. The maximum temperature of the reactionsolution in the polymerization step (Z) is shown in Table 7.

Example 5-6 Production of Conductive Aniline Polymer (P2-3)

A conductive aniline polymer (P2-2′) solution was obtained in the samemanner as in Example 5-5.

To 50 g of the obtained conductive aniline polymer (P2-2′) solution,102.9 g of an aqueous solution of 1 mol/L ammonium peroxodisulfatecontaining 0.005 mol of 98% by mass sulfuric acid, and 0.025 mol of2-aminoanisole-4-sulfonic acid dissolved in 70.3 g of 4.5 mol/Ltriethylamine aqueous solution were each simultaneously added dropwiseover 2 hours. In the reaction, the temperature of the refrigerant wasadjusted so that the temperature of the reaction solution was −5° C.

After completion of the dropwise addition, while the temperature of therefrigerant was adjusted so that the temperature of the reactionsolution was −5° C., the reaction solution was kept at that temperaturefor 4 hours under stirring at a stirring rotation speed of 200 rpm(polymerization step (Z2-2)). Thus, a conductive aniline polymer (P2-3)solution was obtained. The maximum temperature of the reaction solutionin the polymerization step (Z2-2) was −4.9° C. when the amount of theadded monomer was 0.1 equivalents.

Each measurement and evaluation of the obtained conductive anilinepolymer (P2-3) was carried out in the same manner as in Example 5-1. Theresults are shown in Table 7. The maximum temperature of the reactionsolution in the polymerization step (Z) is shown in Table 7.

Example 5-7 Production of Conductive Aniline Polymer (P2-4)

A conductive aniline polymer (P2-3) solution was obtained in the samemanner as in Example 5-6.

To 50 g of the obtained conductive aniline polymer (P2-3) solution,102.9 g of an aqueous solution of 1 mol/L ammonium peroxodisulfatecontaining 0.005 mol of 98% by mass sulfuric acid, and 0.025 mol of2-aminoanisole-4-sulfonic acid dissolved in 70.3 g of 4.5 mol/Ltriethylamine aqueous solution were each simultaneously added dropwiseover 2 hours. In the reaction, the temperature of the refrigerant wasadjusted so that the temperature of the reaction solution was −5° C.

After completion of the dropwise addition, while the temperature of therefrigerant was adjusted so that the temperature of the reactionsolution was −5° C., the reaction solution was kept at that temperaturefor 4 hours under stirring at a stirring rotation speed of 200 rpm(polymerization step (Z2-3)). Thus, a conductive aniline polymer (P2-4)solution was obtained. The maximum temperature of the reaction solutionin the polymerization step (Z2-3) was −4.9° C. when the amount of theadded monomer was 0.1 equivalents.

Each measurement and evaluation of the obtained conductive anilinepolymer (P2-4) was carried out in the same manner as in Example 5-1. Theresults are shown in Table 7. The maximum temperature of the reactionsolution in the polymerization step (Z) is shown in Table 7.

TABLE 7 Maximum temperature Film of reaction Molecular Area thick-Conduc- solution mass ratio ness tivity Polymerization step (Z) (° C.)(M) (X/Y) (nm) (S/cm) Example (1) main reaction: 1.5 34900 1.39 104 4.85-3 production of (P2-1) (addition and retention) Example (1) mainreaction: 1.5 36200 1.29 99 6.3 5-4 production of (P2-1) (addition andretention) (2) additional reaction: production of (P2-2) (addition)Example (1) main reaction: 1.5 52000 1.59 97 15.9 5-5 production of(P2-1) (addition and retention) (2) additional reaction: production of(P2-2’) (addition and retention) Example (1) main reaction: 1.5 571002.10 100 21.8 5-6 production of (P2-1) (addition and retention) (2)additional reaction: production of (P2-2’) (addition and retention) (3)additional reaction: production of (P2-3) (addition and retention)Example (1) main reaction: 1.5 64200 2.51 107 23.5 5-7 production of(P2-1) (addition and retention) (2) additional reaction: production of(P2-2’) (addition and retention) (3) additional reaction: production of(P2-3) (addition and retention) (4) additional reaction: production of(P2-4) (addition and retention)

As shown in Table 7, the area ratios (X/Y) of the conductive anilinepolymers (P2-1), (P2-2), (P2-2′), (P2-3), and (P2-4) obtained inExamples 5-3 to 5-7 were 1.20 or more. The conductive aniline polymershad high conductivity. Among them, the conductive aniline polymers(P2-2), (P2-2′), (P2-3), and (P2-4) obtained in Examples 5-4 to 5-7, inwhich additional polymerization was carried out, had higher conductivityas compared with the conductive aniline polymer (P2-1) obtained inExample 5-3 without additional polymerization. Thus, the conductivitiesof the polymers were improved. In particular, in Examples 5-5 to 5-7, inwhich the reaction solution was kept in the polymerization step (Z2),the conductivities were further enhanced. as the larger the number ofadditional polymerization was, the higher the conductivity was, andtherefore the conductivity tended to be further enhanced.

Example 6-1

A conductive aniline polymer (P2-2) solution was obtained in the samemanner as in Example 5-4.

The solid content concentration in the obtained conductive anilinepolymer (P2-2) solution was adjusted to 5% by mass. Then, 5 g of thissolution was passed through a column with a diameter of 1 cm, filledwith 5 mL of Amberlite IR-120 B(H) (available from Organo Corporation)to perform cationic exchange (demineralization). The thermal resistancewas evaluated using the conductive aniline polymer after thedemineralization. The result is shown in Table 8.

Example 6-2

The demineralization and evaluation of thermal resistance were carriedout in the same manner as in Example 6-1 using the conductive anilinepolymer (P2-2′) solution produced in Example 5-5. The results are shownin Table 8.

Example 6-3

The demineralization and evaluation of thermal resistance were carriedout in the same manner as in Example 6-1 using the conductive anilinepolymer (P2-3) solution produced in Example 5-6. The results are shownin Table 8.

Example 6-4

The demineralization and evaluation of thermal resistance were carriedout in the same manner as in Example 6-1 using the conductive anilinepolymer (P2-4) solution produced in Example 5-7. The results are shownin Table 8.

TABLE 8 Conductivity Molecular Area ratio after heating mass (M) (X/Y)(S/cm) Example 6-1 36200 1.29 0.11 Example 6-2 52000 1.59 0.47 Example6-3 57100 2.10 1.02 Example 6-4 64200 2.51 2.97

In Examples 6-1 to 6-4, in which the area ratio (X/Y) is 1.20 or more asshown in Table 8, even when the conductive aniline polymer solution wasdried by heating at 60° C. for 1 hour, the conductivity could bemaintained. Further, the conductive aniline polymer solution had thermalresistance. In particular, the larger the molecular mass (M) was, and/orthe larger the area ratio (X/Y) was, the higher the conductivity was,and therefore, the thermal resistance was more excellent.

DESCRIPTION OF REFERENCE SIGNS

-   x: region (x)-   y: region (y)

1. A conductive aniline polymer comprising a repeating unit representedby formula (1) and having an area ratio X/Y of 1.20 or more, which iscalculated by: (I) preparing a test solution by dissolving a conductiveaniline polymer in an eluent adjusted to pH 10 or more so that a solidcontent concentration of the conductive aniline polymer in the testsolution is 0.1% by mass; (II) subjecting the test solution to a polymermaterials evaluation system equipped with a gel permeation chromatographto determine a molecular mass distribution of the test solution toobtain a chromatogram thereof; (III) converting the retention time inthe chromatogram obtained in (II) to a molecular mass M in terms ofsodium polystyrene sulfonate; (IV) determining an area X of a regionhaving a molecular mass of 15,000 Da or more in the converted molecularmass M in terms of sodium polystyrene sulfonate; (V) determining an areaY of a region having a molecular mass of less than 15,000 Da in theconverted molecular mass M in terms of sodium polystyrene sulfonate; and(VI) determining the area ratio X/Y of the area X to the area Y,

wherein R¹ to R⁴ are each independently —H, a linear or branched alkylgroup having 1 to 24 carbon atoms, a linear or branched alkoxy grouphaving 1 to 24 carbon atoms, an acidic group or a salt thereof, ahydroxy group, a nitro group, —F, —Cl, —Br, or —I; and at least one ofR¹ to R⁴ is an acidic group or a salt thereof, provided that the acidicgroup is a sulfonic acid group or a carboxyl group.
 2. A method forproducing the conductive aniline polymer of claim 1, comprising apolymerizing Z1 where an aniline derivative A represented by formula (2)is polymerized in a solution containing a basic compound B, a solvent C,and an oxidizing agent D at a temperature lower than 25° C.,

wherein R⁵ to R⁹ are each independently —H, a linear or branched alkylgroup having 1 to 24 carbon atoms, a linear or branched alkoxy grouphaving 1 to 24 carbon atoms, an acidic group or a salt thereof, ahydroxy group, a nitro group, —F, —Cl, —Br, or —I; and at least one ofR⁵ to R⁹ is an acidic group or a salt thereof; provided that the acidicgroup is a sulfonic acid group or a carboxyl group.
 3. The method ofclaim 2, wherein the solvent C comprises 35% by volume or more of waterrelative to an entire volume of the solvent C.
 4. A method for producingthe conductive aniline polymer of claim 1, comprising a polymerizing Z2where an aniline derivative A represented by the formula (2) and anoxidizing agent D are added to and polymerized in a solution in whichthe conductive aniline polymer is dissolved in a solvent C, or added toand polymerized in a dispersion in which the conductive aniline polymeris dispersed in the solvent C,

wherein R⁵ to R⁹ are each independently —H, a linear or branched alkylgroup having 1 to 24 carbon atoms, a linear or branched alkoxy grouphaving 1 to 24 carbon atoms, an acidic group or a salt thereof; ahydroxy group, a nitro group, —F, —Cl, —Br, or —I; and at least one ofR⁵ to R⁹ is an acidic group or a salt thereof; provided that the acidicgroup is a sulfonic acid group or a carboxyl group.
 5. The method ofclaim 4, wherein the solvent C comprises 35% by volume or more of waterrelative to an entire volume of the solvent C.
 6. The method of claim 2,further comprising purifying a solution comprising a product obtained inthe polymerizing Z1 by membrane filtration.
 7. The method of claim 2,further comprising purifying a solution comprising a product obtained inthe polymerizing Z1 by precipitation.
 8. The method of claim 7, furthercomprising purifying by membrane filtration a solution comprising apurified substance obtained in the precipitation.
 9. A method forproducing a conductive film comprising applying a solution comprisingthe conductive aniline polymer of claim 1 to a base material and dryingthe solution applied to the base material.
 10. The method of claim 2,wherein a starting polymerization reaction temperature of the solutionis less than 5° C., and a maximum polymerization temperature is lessthan 25° C.
 11. The method of claim 10, wherein the solvent C comprises35% by volume or more of water relative to an entire volume of thesolvent C.
 12. The method of claim 3, further comprising purifying asolution comprising a product obtained in the polymerizing Z1 bymembrane filtration.
 13. The method of claim 4, further comprisingpurifying a solution comprising a product obtained in the polymerizingZ2 by membrane filtration.
 14. The method of claim 5, further comprisingpurifying a solution comprising a product obtained in the polymerizingZ2 by membrane filtration.
 15. The method of claim 3, further comprisingpurifying a solution comprising a product obtained in the polymerizingZ1 by precipitation.
 16. The method of claim 4, further comprisingpurifying a solution comprising a product obtained in the polymerizingZ2 by precipitation.
 17. The method of claim 5, further comprisingpurifying a solution comprising a product obtained in the polymerizingZ2 by precipitation.
 18. The method of claim 15, further comprisingpurifying by membrane filtration a solution comprising a purifiedsubstance obtained in the precipitation.
 19. The method of claim 16,further comprising purifying by membrane filtration a solutioncomprising a purified substance obtained in the precipitation.
 20. Themethod of claim 17, further comprising purifying by membrane filtrationa solution comprising a purified substance obtained in theprecipitation.